Manufacturing method of semiconductor substrate and method and apparatus for inspecting defects of patterns of an object to be inspected

ABSTRACT

A pattern detection method and apparatus thereof for inspecting with high resolution a micro fine defect of a pattern on an inspected object and a semiconductor substrate manufacturing method and system for manufacturing semiconductor substrates such as semiconductor wafers with a high yield. A micro fine pattern on the inspected object is inspected by irradiating an annular-looped illumination through an objective lens onto a wafer mounted on a stage, the wafer having micro fine patterns thereon. The illumination light may be circularly or elliptically polarized and controlled according to an image detected on the pupil of the objective lens and image signals are obtained by detecting a reflected light from the wafer. The image signals are compared with reference image signals and a part of the pattern showing inconsistency is detected as a defect so that simultaneously, a micro fine defect or defects on the micro fine pattern are detected with high resolution. Further, process conditions of a manufacturing line are controlled by analyzing a cause of defect and a factor of defect which occurs on the pattern.

FIELD OF THE INVENTION

[0001] The present invention relates to a manufacturing method of asemiconductor substrate such as a semiconductor wafer, a TFT (Thin FilmTransistor) liquid crystal substrate, a thin film multi-layer substrateand a printed board, which have respectively micro fine circuit patternsor wiring patterns, at a high yield rate, a method and apparatus formeasuring highly precise dimensions of patterns to be inspected, whichcomprises micro fine circuit patterns or wiring patterns formed on theobject to be inspected such as the semiconductor wafer, the TFT liquidcrystal substrate, the thin film multi-layer substrate and the printedboard and inspecting the patterns on the object to be inspected, amethod and apparatus for detecting micro fine defects of the patterns onthe object to be inspected, and a microscope to be used in theaforementioned detection method.

BACKGROUND OF THE INVENTION

[0002] Recently, the patterns to be inspected, each comprising circuitpatterns or wiring patterns formed on, for example, the semiconductorwafer, the TFT liquid crystal substrate, the thin film multi-layersubstrate and the printed board have been adapted to be furthermicro-structured in response to the needs for high density integration.Since the circuit patterns or the wiring patterns are furthermicro-structured along with high density integration, a defect whichshould be detected becomes smaller or finer. Detection of such microfine defects has been an extremely important subject in determination ofan integrity of the circuit patterns or the wiring patterns inmanufacturing of the circuit patterns or the wiring patterns.

[0003] However, the above-described micro structure has been furtheradvanced and detection of micro fine defects of the patterns to beinspected such as the circuit patterns or the wiring patterns hasreached the limit of resolution of the imaging optical system, andtherefore essential improvement of the resolution has been demanded.

[0004] A prior art apparatus for essentially improving the resolution isdisclosed in Japanese Patent Laid-Open No. Hei 5-160002. In thisdocument, there is disclosed a pattern inspection apparatus whichcomprises an illumination arrangement for providing an annular-loopeddiffusion illumination formed with arrays of a plurality of virtual spotlight sources for micro fine circuit patterns which is formed on a mask,through light source space filters, a light receiving arrangement havingan optical pupil which sufficiently introduces a diffraction light fromthe micro fine pattern, which passes through or reflected from a maskwhich is almost uniformly diffusion-illuminated by the illuminationarrangement and has imaging space filters for shutting off at least partof 0th order diffraction light or low order diffraction light of thisintroduced light, to obtain image signals by receiving the circuitpattern imaged through the optical pupil, and a comparison arrangementfor comparing the image signals obtained by the light receivingarrangement with mask pattern data or wafer pattern data or data from atransfer simulator to inspect the pattern. In this document, there isalso disclosed a method for controlling a shape of a light source apacefilter and an imaging space filter in accordance with the pattern shapedata.

[0005] However, there has been a problem that, though, in theabove-described prior art with respect to detection of a defect of themicro fine pattern. That is, although a defect of the micro fine patternis detected by applying the annular-looped diffusion illumination to themicro fine pattern on the object to be inspected and sufficientlyintroducing the diffraction light from the micro fine pattern into theopening (pupil) of the objective lens to obtain high resolution imagesignals, full consideration has not been taken for the point that amicro fine defect should be detected with high reliability in responseto various micro fine patterns existing on the object to be inspected.

[0006] Further, full consideration has also not been given formanufacturing semiconductor substrates having micro fine patterns suchas a semiconductor wafer, a TFT liquid crystal substrate, a thin filmmulti-layer substrate and a printed board with reduced defects and highyield rate.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to solve the above problemsof the prior art and to provide a method for manufacturing semiconductorsubstrates which is adapted to manufacture semiconductor substrates suchas, for example, a semiconductor wafer, a TFT liquid crystal substrate,a thin film multi-layer substrate and a printed board, each having microfine patterns, in a high yield rate.

[0008] Another object of the present invention is to provide a patterndetection method for detecting a pattern on an object to be inspectedand an apparatus thereof (microscope system) which are adapted to detecta defect of a micro fine pattern with high reliability in response tovarious micro fine patterns provided on objects to be inspected such asa semiconductor wafer, a TFT liquid crystal substrate, a thin filmmulti-layer substrate, and a printed board.

[0009] A further another object of the present invention is to provide amethod and an apparatus for inspecting a defect of a pattern on theobject to be inspected which are adapted to inspect a micro fine defectof a micro fine pattern with high reliability in response to variousmicro fine patterns provided on objects to be inspected such as asemiconductor wafer, a TFT liquid crystal substrate, a thin filmmulti-layer substrate, and a printed board.

[0010] To achieve the above objects, a semiconductor substratemanufacturing method for manufacturing semiconductor substrates eachhaving patterns formed by a manufacturing line comprising variousprocess units, according to the present invention comprises: a historydata or data base build-up step for building up history data or database which shows a relation of causes and effects by accumulating inadvance the history data or data base showing the relation of defectinformation of a pattern which appears on the semiconductor substrat anda cause of defect or a factor of defect which causes a defect of thepattern in the manufacturing line; a defect inspection step fordetecting the defect information of the pattern by comparing imagesignals of the pattern on the semiconductor substrate with image signalsof the reference pattern, for the semiconductor substrate which hasreached a specified position of the manufacturing line; a defectanalyzing step for analyzing a cause of defect or a factor of defectwhich causes a defect of the pattern in the manufacturing line locatedat an upper stream from the specified position of the manufacturingline, according to the defect information of the pattern detected in thedefect inspection step and the history data or the data base which showsthe relation of causes and effects, built up in the history data or database build-up step; and a process condition control step for controllingprocess conditions in the above-described upper stream manufacturingline to eliminate the cause of defect or the factor of defect analyzedin the defect analyzing step.

[0011] With the configuration described above, the present inventionenables inspection of micro fine defects with high resolution and highsensitivity on semiconductor substrates such as the semiconductor wafer,the TFT substrate, the thin film multi-layer substrate and the printedboard each having micro fine patterns (for example, patterns the pitchof which is 1 μm or under (0.8 to 0.4 μm)), to reduce the number ofmicro fine defects on the semiconductor substrates by feeding back theresults of inspection to the manufacturing processes for semiconductorsubstrates, and to manufacture the semiconductor substrates having microfine patterns with a high yield rate.

[0012] According to the present invention, for materializing amanufacturing method of the semiconductor substrate, a method andapparatus for detecting a defect of the patterns on the object to beinspected are adapted to detect the pattern on the object to beinspected according to the image signals of the pattern on the object tobe inspected which are obtained by concentrating an annular-loopeddiffusion illumination light formed by a plurality of virtual spot lightsources and irradiating the illumination light onto the pattern on theobject to be inspected through the pupil of the objective lens. Theabove configuration enables sufficient introduction of the reflectedlight which is obtained by slantly or obliquely introducing a focusedillumination light from, for example, the annular-looped illuminationonto a semiconductor substrate (object to be inspected), into theopening (pupil) of the objective lens and consequently obtain imagesignals of a pattern having a sufficient resolution, identify thereflected light by monitoring an image on the pupil plane of theobjective lens, and detect the image signals of the pattern with thesufficient resolution and a large depth of the focus under an optimumcondition at all times in response to a micro fine pattern by, forexample, controlling the annular-looped illumination. By detecting alocalization distribution or an intensity distribution of the reflectedlight from the image of the pupil plane (Fourier transformation plane)and controlling the annular-looped illumination in accordance with thelocalization distribution or the intensity distribution (correspondingto the density of pattern) of the detected diffraction light, thepattern can be sufficiently inspected with a normal resolution by theannular-looped illumination under the preset condition since the patterndensity is not so high in a case of, for example, a 4 Mb DRAM memorydevice and the pattern can be inspected with the annular-loopedillumination which provides a higher resolution under the presetcondition in a case of, for example, a 16 Mb DRAM memory device. Inaddition, the pattern can be inspected with high resolution by using theannular-looped illumination under the preset condition since the patterndensity is high at, for example, the cell part of the memory device andthe pattern can be inspected at a high speed by using a normalillumination since the inspection sensitivity can be lowered in a rougharea other than the cell part.

[0013] Furthermore, for implementing the above-described semiconductorsubstrate manufacturing method, a method and apparatus for inspecting adefect of a pattern on the object to be inspected according to thepresent invention are adapted to concentrate and irradiate theannular-looped diffusion illumination light comprising a number ofvirtual spot light sources onto the pattern on the object to beinspected through the pupil of the objective lens, compare an imagesignal obtained therefrom of the pattern on the inspected object withthe image signal of the reference pattern, and erase the pattern on theinspected object when these image signals coincide and detect a defectwhen these image signals do not coincide.

[0014] The above-described configuration enables detection of highdefinition (high resolution) image signals from micro fine patterns andinspection of a defect on the micro fine pattern with high reliabilitysince the high definition image signals can be compared with the highdefinition reference image signals with respect to a chip or cell.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a block diagram arrangement showing an embodiment of aninspection apparatus according to the present invention for inspecting adefect of the pattern on the object to be inspected;

[0016]FIG. 2 is a schematic illustration of a disc type mask(annular-looped secondary light source) in the embodiment shown in FIG.1;

[0017]FIG. 3 is a schematic illustration showing in detail the maskelement of the disc type mask shown in FIG. 2;

[0018]FIG. 4 is a schematic illustration showing further in detail themask element of the disc type mask shown in FIG. 2;

[0019]FIG. 5 is an illustration showing practical dimensions of the maskelement shown in FIG. 4;

[0020]FIG. 6 is an illustration showing a grid pattern to be repeated inthe X axis direction which is an embodiment of an LSI wafer pattern;

[0021]FIG. 7 is an X-Y plan view on the pupil of the objective lens,showing 0th order diffraction light and first order diffraction lightwhich are produced in the X axis direction from the grid pattern shownin FIG. 6 by casting the annular-looped illumination onto the gridpattern to be incident onto the pupil of the objective lens;

[0022]FIG. 8 is an X-Z cross sectional view showing the 0th orderdiffraction light and the first order diffraction light which areproduced from the annular-looped illumination and the grid pattern shownin FIG. 7 to be incident onto the pupil of the objective lens;

[0023]FIG. 9 is an X-Y plan view on the pupil of the objective lens,showing 0th order diffraction light and first order diffraction lightwhich are produced in the Y axis direction from the grid pattern shownin FIG. 6 by casting the annular-looped illumination onto the gridpattern to be incident onto the pupil of the objective lens;

[0024]FIG. 10 is an X-Y plan view on the pupil of the objective lens,showing 0th order diffraction light and first order diffraction lightwhich are produced in X and Y axis directions from the grid patternshown in FIG. 6 by casting the annular-looped illumination onto the gridpattern to be incident onto the pupil of the objective lens;

[0025]FIG. 11 is an illustration showing the relationship between thevalue σ and the incident angle ψ of the objective lens;

[0026]FIG. 12 is an illustration showing the relationship between theincident angle ψ and the diffraction angle θ;

[0027] FIGS. 13(a) and 13(b) are illustrations of a linear diagramshowing a situation where + first order diffraction light is producedwhen the annular-looped illumination with the wavelength of λ=0.4 to 0.6μm and the value σ of 0.60 to 0.40 is cast to a grid pattern of P=0.61μm;

[0028] FIGS. 14(a) and 14(b) are illustrations a linear diagram showinga situation where + first order diffraction light is produced when theannular-looped illumination with the wavelength of λ=0.4 to 0.6 μm andthe value σ of 0.60 to 0.40 is cast to a grid pattern of P=0.7 μm;

[0029]FIG. 15 is an illustration showing a grid pattern to be repeatedin the Y axis direction which is an embodiment of the LSI wafer pattern;

[0030]FIG. 16 is an X-Y plan view on the pupil of the objective lens,showing 0th order diffraction light and first order diffraction lightwhich are produced in the Y axis direction from the grid pattern shownin FIG. 15 by casting the annular-looped illumination onto the gridpattern to be incident onto the pupil of the objective lens;

[0031]FIG. 17 is an Y-Z cross sectional view showing a state ofattenuation of 0th order diffraction light through an attenuation filter(light quantity control filter);

[0032]FIG. 18 is an X-Y plan view on the pupil conjugated with the pupilof the objective lens showing a state of attenuation of the 0th orderdiffraction light through the attenuation filter (light quantity controlfilter) for which the contents shown in FIG. 17 are provided at aposition conjugated with the pupil of the objective lens;

[0033]FIG. 19 is an illustration showing a cross sectional shape of theattenuation filter (light quantity control filter) and itstransmissivity characteristic when the transmissivity is set to beapproximately 0;

[0034]FIG. 20 is an illustration showing a cross sectional shape of theattenuation filter (light quantity control filter) and itstransmissivity characteristic when the transmissivity is set to beapproximately 0.2;

[0035]FIG. 21 is a diagram showing an embodiment in which a light houseis controlled in the optical axis direction for a collimator lens in theannular-looped illumination according to the present invention;

[0036]FIG. 22 is a diagram showing an embodiment in which a collimatorlens is controlled in the optical axis direction for a light house lensin the annular-looped illumination according to the present invention;

[0037]FIG. 23 is a block diagram arrangement showing an embodiment of amicroscope system according to the present invention;

[0038]FIG. 24 is a diagram showing various defects in a wafer patternaccording to the present invention;

[0039]FIG. 25 is an illustration showing the relation to the dimensionsof the pixel to be detected at a portion on the wafer pattern shown inFIG. 24;

[0040] FIGS. 26(a) and 26(b) show the pattern at the portion shown inFIG. 25 and an image signal waveform corresponding to the brightnesswhich faithfully represents this pattern;

[0041] FIGS. 27(a) and 27(b) show an image signal corresponding to asampled brightness obtained by sampling image signals corresponding tothe brightness shown in FIG. 26;

[0042] FIGS. 28(a) and 28(b) show an image signal waveform correspondingto a brightness which is faithfully obtained when the size of the pixelto be detected is set to 0.0175 μm for a grid repetitive patterncomprising lines of 0.42 μm in width and spaces;

[0043] FIGS. 29(a) and 29(b) show an image signal waveform correspondingto a brightness for which a maximal value is maintained when the size ofthe pixel to be detected is set to 0.14 μm for a grid repetitive patterncomprising lines of 0.42 μm in width and spaces;

[0044] FIGS. 30(a) and 30(b) show an image signal waveform correspondingto a brightness for which a maximal value is not maintained when thesize of the pixel to be detected is set to 0.28 μm for a grid repetitivepattern comprising lines of 0.42 μm in width and spaces;

[0045]FIG. 31 illustrates an optical system in an embodiment of thepattern inspection apparatus shown in FIG. 1 according to the presentinvention for inspecting a defect of the pattern on the object to beinspected;

[0046]FIG. 32 is a front view of FIG. 31;

[0047]FIG. 33 is a plan view further specifically showing the embodimentshown in FIG. 31;

[0048]FIG. 34 is a front view of FIG. 33;

[0049]FIG. 35 is a diagram showing an embodiment of an optical systemfor circular polarization illumination;

[0050]FIG. 36 is a diagram for describing conversion from linearpolarization to circular or elliptic polarization with a ¼ wavelengthplate;

[0051]FIG. 37 shows a detection intensity corresponding to thebrightness for a pattern angle in an experimental example for which astate of polarization in the annular-looped illumination is controlled;

[0052]FIG. 38 shows a contrast for a pattern angle in an experimentalexample for which a state of polarization in the annular-loopedillumination is controlled; and

[0053]FIG. 39 is a block diagram arrangement for describingmanufacturing of semiconductor substrates at a high yield rate byanalyzing causes of defect or factors of defect with an analyticalcomputer according to the present invention and feeding back the causesof defect or the factors of defect which has been analyzed to theprocess units in a manufacturing line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] Referring now to the drawings, like reference numerals areutilized to designate like parts throughout so that detailed descriptionof the like parts are omitted with embodiments according to the presentinvention for detection of a pattern on an object to be inspected andinspection of a defect on the pattern being described, referring toFIGS. 1 to 39, and an embodiment according to the present invention inwhich inspection of a defect on the object to be inspected is applied tosemiconductor manufacturing processes being described referring to FIG.39. In the embodiments, an annular-looped illumination (annular-loopeddiffusion illumination) is utilized for providing substantially uniformillumination in a field of detection of the object to be inspectedthrough an objective lens is described below.

[0055]FIG. 1 is a block diagram showing a first embodiment of a patterninspection apparatus using annular-looped illumination according to thepresent invention comprising an object to be inspected (a pattern to beinspected) 1 such as an LSI wafer for pattern inspection; an XYZθ stage2 on which the object to be inspected 1 such as the LSI wafer ismounted; a secondary light source for annular-looped illumination whichincludes a xenon (Xe) lamp 3 for a light source, an elliptic mirror 4for focusing a light and a disc type mask 5 (secondary light source forannular-looped illumination) for forming an annular-looped illumination(annular-looped diffusion illumination) for forming an annular-loopedsecondary light source which includes a plurality of virtual spot lightsources; an illumination optical system including a collimator lens 6, alight quantity control filter 14 and a condenser lens 7; a patterndetection optical system which includes half mirrors 8 a and 8 b, anobjective lens 9, a focusing lens 11, a zoom lens 13 provided with anattenuation filter 38 on a pupil plane 10 b conjugated with the pupilplane 10 a of the objective lens 9 and two-dimensional orone-dimensional image sensors 12 a and 12 b; and an image processing andcontrolling system for detection of defects, which includes A/Dconverters 15 a and 15 b for converting image signals detected from theimage sensors 12 a and 12 b to digital image signals, a delay memory 16for storing digital image signals obtained from the A/D converter 15 aand delaying these image signals, a comparator circuit 17 for comparingdelayed digital image signals stored in the delay memory 16 and digitalimage signals obtained from the A/D converter 15 a, an edge detector 21for detecting an edge of the pattern from the digital image signalsobtained from the A/D converter 15 a, and a CPU 20 which carries out thecontrol of the disc type mask 5 for forming the annular-loopedillumination which is the secondary light source based on a movingmechanism 19 and the control of the attenuation filter 38 based on amoving mechanism 39 in accordance with the digital image signals on thepupil plane 10 a of the objective lens 9 obtained from the image sensor12 b, which detects the image of the pupil plane 10 a of the objectivelens 9 through the A/D converter 15 b, carries out the comparison in thecomparator circuit 17 in accordance with the edge signal to be detectedby the edge detector 21 and carries out the control of the XYZθ stage 2based on a driver 45.

[0056] A defect determination output 18 is obtained from the comparatorcircuit 17 and is also entered into the CPU to be added with a defectoccurring position (coordinates) on the object 1 to be inspected and isstored in storage arrangement (not shown) for at least a unit of theinspected object 1 and a unit of a plurality of inspected objects 1sampled from a specified manufacturing process. Defect information 40 inat least the unit of the inspected object 1 and the process unit of theinspected object 1 sampled from the specified manufacturing processwhich is stored in this storage means is outputted from the CPU 20. Thisdefect information 40 includes the defect occurring position(coordinates) on the inspected object 1 obtained based on the defectdetermination output 18 and a type of defect (projection defect 231,chipping defect 236, opening defect 232, short-circuiting defect 234,discoloration defect 233, stain defect 235, etc., as shown in FIG. 24,for example) which is classified according to the defect determinationoutput 18 in the CPU 20 as shown in FIG. 23. The types of these defectsneed not always be definitely classified.

[0057] In FIG. 1, a light house 124 is formed with the Xe lamp 3 whichis the primary light source, the elliptic mirror 4 for focusing a lightemitted from the Xe lamp 3 and the disc type mask 5 comprising aplurality of virtual spot light sources, for forming the annular-loopedillumination as the secondary light source. The moving mechanism 19 isprovided to rotate the disc type mask (secondary light source forannular-looped illumination) 5 in steps according to a command from theCPU 20 and to change over a different type annular-looped illumination(if there is no IN σ as shown, for example, in FIG. 3, it is similar tonormal illumination). The disc type mask 5 is the annular-loopedsecondary light source formed by a plurality of virtual spot lightsources and an annular-looped diffusion illumination is obtained fromthis annular-looped secondary light source.

[0058] Accordingly, the annular-looped illumination emitted from thedisc type mask (secondary light source for annular-looped illumination)5 is focused as an incident illumination light 24 onto the pupil 10 a ofthe objective lens 9 through the collimator lenses 6 and 7 as shown inFIGS. 7, 9 and 10, and this focused incident illumination light isfocused by the objective lens 9 and irradiated onto the inspected object1 such as an LSI wafer set on the XYZθ stage 2 (the θ stage not beingshown). The light quantity control filter 14 serves to adjust a lightquantity to be irradiated onto the inspected object 1. A drive mechanism14 a for driving the light quantity adjusting filter 14 is controlled inaccordance with a command from the CPU 20.

[0059] A 0th order reflected diffraction light (positive reflectionlight), and first order and second order reflected diffraction lights atthe + and − sides are produced from the pattern on the inspected object1 such as the LSI wafer. Thus, of the 0th order reflected diffractionlight (positive reflection light) and + and − side first order andsecond order reflected diffraction lights produced as described above, areflected diffraction light which is introduced into the pupil 10 a ofthe objective lens 9 is reflected from the half mirrors 8 a and 8 b tobe incident onto the pupil 10 b of the zoom lens 13 and this reflecteddiffraction light is focused onto the image sensor 12 a by the zoom lens13. The image sensor 12 a receives the reflected diffraction light whichis produced from the pattern on the inspected object 1 such as the LSIwafer and introduced to be incident into the pupil 10 a of the objectivelens 9, and outputs an image signal representing the reflecteddiffraction light of the pattern of the inspected object 1. The pupil 10a of the objective lens 9 and the pupil 10 b of the zoom lens 13 have aconjugating relationship. The 0th order diffraction light introducedinto the pupil 10 a of the objective lens 9 can be attenuated by theattenuation filter 38 on the pupil 10 b of the zoom lens 13 as required.

[0060] On the other hand, the reflected diffraction light introducedinto the pupil 10 a of the objective lens 9 is focused onto the imagesensor 12 b through the focusing lens 11. Accordingly, the image sensor12 b receives the reflected diffraction light introduced into the pupil10 a of the objective lens 9 and outputs the image signal of thisreflected diffraction light to permit detection of a state of thereflected diffraction light incident into the pupil 10 a of theobjective lens 9. In other words, if the periodicity of the pattern onthe inspected object 1 such as the LSI wafer changes as shown in FIGS.13 and 14, the mode of the first order diffraction light to the incidentillumination light 24 also changes and the first order diffraction lightincident into the pupil 10 a of the objective lens 9 changessimultaneously. FIG. 13 shows a case where the density (periodicity) ofthe pattern on the inspected object 1 is high and FIG. 14 shows a casewhere the density (periodicity) of the pattern on the inspected object 1is low. If the pitch P (density or periodicity) of the pattern on theinspected object 1 or the wavelength λ of the incident illuminationlight 24 is changed, it is known from a relation presented by equation 2that the diffraction angle θ of the first order diffraction light to theincident angle ψ of the incident illumination light 24 changes and thefirst order diffraction light incident into the pupil 10 a of theobjective lens 9 also changes.

[0061] If the type of the inspected object 1 such as, for example, theLSI wafer is changed, the pitch P (density or periodicity) of thepattern thereon also changes. If the type of the LSI wafer is changedto, for example, 256M DRAM or 64M DRAM, the pitch P (density orperiodicity) of the pattern also changes. If the process is changed eventhough the types are of the same, the density (periodicity) of thepattern may change, for example, the pitch P of the pattern of theinspected object in the wiring process or the diffusion process changes.In one chip on the LSI wafer, the pitches P of the patterns of thememory and the peripheral circuit differ from each other.

[0062] It is necessary to change the wavelength λ of the incidentillumination light 24 in accordance with the cross sectional structureof the inspected object 1. For example, a thickness of a thin film whichforms the inspected object 1 varies and therefore the reflected lightfrom the inspected object is caused to change due to an opticalinterference in the thin film. To avoid such variation of the reflectedlight, it is necessary to change the wavelength λ of the incidentillumination light 24 to select the wavelength λ of the incidentillumination light 24 with which the optical interference hardly occursin the thin film. For example, as shown in other embodiments describedlater, the wavelength λ of the incident illumination light 24 can bechanged through a wavelength selection filter by using a light sourcewhich emits lights, respectively, having a plurality of types ofwavelength in the illumination optical system.

[0063] If the pitch P (density or periodicity) of the pattern on theinspected object 1 or the wavelength λ of the incident illuminationlight 24 is changed, the diffraction angle θ of the first orderdiffraction light to the incident angle ψ of the incident illuminationlight 24 changes and the first order diffraction light incident into thepupil 10 a of the objective lens 9 also changes. Therefore, the value σof the secondary light source for annular-looped illumination, that is,the incident angle ψ of the illumination light 24 to the inspectedobject 1 should be controlled in accordance with the type or the crosssectional structure of the inspected object 1 so that, particularly, thefirst order diffraction light of the diffraction lights produced fromthe inspected object is introduced into the pupil 10 a of the objectivelens 9 in an optimal condition.

[0064] Therefore, the CPU 20 carries out a Fourier transform imageanalysis of digital Fourier transform image signals on the pupil 10 a(Fourier transform plane) of the objective lens 9 obtained from theimage sensor 12 b through the A/D converter 15 b and edge densitydetermination (periodicity or density determination of the pattern onthe inspected object 1) according to the results of this Fouriertransform image analysis, and selects the secondary light source 5 (asshown, for example, in FIGS. 3 and 4; FIG. 4 includes an ordinary lightsource with IN σ of 0) for the optimum annular-looped illumination bydriving the moving mechanism 19 so that the digital image signal of thereflected diffraction light introduced into the pupil 10 a of theobjective lens 9, that is, the 0th order and first order diffractionlights from the pattern on the inspected object 1 are sufficientlyintroduced into the pupil 10 a of the objective lens 9 to obtainfaithful image signals from the pattern on the inspected object 1 fromthe image sensor 12 a.

[0065] Illumination is the so-called Koehler illumination free ofunevenness. Although not shown, the illumination light is focused sothat the image of the reflected diffraction light from the pattern onthe inspected object 1 such as the LSI wafer is clearly formed in theimage sensor 12 a. In other words, the pattern (surface) on theinspected object 1 such as the LSI wafer is automatically focused to thedetection optical system.

[0066] Two-dimensional image signals of the pattern on the inspectedobject 1 can be obtained from the image sensor 12 a by scanning to pickup the pattern image with the image sensor 12 a while moving the X stageon which the inspected object 1 such as the LSI wafer is set. In thiscase, the X stage can be moved in continuous feed, step feed or repeatedfeed.

[0067] The two-dimensional image signals obtained as described above areA/D-converted by the A/D converter 15 a, two-dimensional digital imagesignals are stored in the delay memory 16 to be delayed while inspectionof the chip or the cell is repeated, and the delayed two-dimensionaldigital image signals and the two-dimensional digital image signalsoutputted from the A/D converter 15 a are compared with respect to thechip or the cell by the comparator circuit 17, and unmatched digitalimage signals are detected as a defect 18.

[0068] The above-described comparator circuit 17 is known in the art andtherefore a detailed description is omitted and it is briefly describedbelow. This comparator circuit 17 is adapted so that two-dimensionallight and dark image signals (digital image signals) obtained from thedelay memory 16 and the A/D converter 15 a with respect to the patternson the inspected object 1 which are formed to be identical aredifferentiation-processed, the positions of two light and dark imagesignals to be compared are aligned so that the number of pixels whosepolarities do not match is not more than a preset value when thepolarities of these light and dark image signals obtained from suchdifferentiation processing are compared, a differential image signal ofthe two light and dark image signals the positions of which are alignedis detected, and a defect is detected by binary-coding this differentialimage signal with a desired threshold value. The comparison processingin this comparator circuit 17 is described in detail in Japanese PatentLaid-Open No. Hei 3-209843.

[0069] The edge detector 21 detects an edge of the pattern on theinspected object 1 according to the two-dimensional digital image signalwhich is detected by the image sensor 12 a and obtained through the A/Dconverter 15 a. The CPU 20 is able to align the positions of two lightand dark image signals (digital image signals) in the comparator circuit17 by fetching the edge information of the pattern on the inspectedobject 1 detected by the edge detector 21 and feeding back theinformation to the comparator circuit 17 and compare these signals withrespect to the chip and the cell by controlling the timing read out fromthe delay memory 16.

[0070] It is apparent that the comparator circuit 17 is not limited tothe above-described configuration and a comparator circuit with anotherconfiguration can be used.

[0071] A two-dimensional digital image signal at a position on thedesignated stage coordinates obtained from the A/D converter 15 a can bestored in the delay memory 16 and the CPU is able to read out andanalyze this signal. Particularly, if the inspected object 1 includes adefect, the characteristics of the defect can be analyzed and thereforethe optimum inspection conditions can be found.

[0072] The disc type mask (secondary light source for annular-loopedillumination) 5 for forming the annular-looped illumination is nowdescribed referring to FIGS. 2 to 5, wherein FIG. 2 is a schematicillustration of the disc type mask (an array of many kinds of maskelements for annular-looped illumination) in the embodiment shown inFIG. 1. FIG. 3 shows a practical embodiment of the disc type mask (anarray of many kinds of mask elements for annular-looped illumination)shown in FIG. 2. FIG. 4 shows another practical embodiment of the disctype mask (an array of many kinds of mask elements for annular-loopedillumination) shown in FIG. 2 and FIGS. 5(a) and 5(b) are diagrams forillustrating the mask element for one annular-looped illumination shownin FIGS. 3 and 4.

[0073] As shown in FIG. 2, mask elements 5-1, 5-2, . . . , 5-n, forexample, for many types of annular-looped illuminations are provided onthe disc type mask 5 and the disc type mask 5 is changed over by themoving mechanism 19 which serves to rotate the disc type mask 5. FIG. 3shows in detail the mask elements 5-1, 5-2, . . . , 5-n for many typesof annular-looped illuminations shown in FIG. 2 with 5 a-1, 5 a-2, . . ., 5 a-n. In FIG. 3, 5a-1 denotes a ring-shaped mask element on which aportion between IN σ and OUT σ is made to be transparent, 5 a-2 shows arinq-shaped mask element on which IN σ and OUT σ are made to be largerthan those of 5 a-1, and 5 a-n shows a ring-shaped mask element in whicha portion of a ring-shaped transparent part is shielded.

[0074]FIG. 4 shows in detail the mask elements 5-1, 5-2, . . . , 5-n formany types of annular-looped illuminations shown in FIG. 2 with 5 b-1, 5b-2, 5 b-3, 5 b-4, 5 b-5, 5 b-6, 5 b-7, 5 b-8, 5 b-9, and 5 a-10. 5 b-1shows a ring-shaped mask element on which a portion between IN σ of 0.6and OUT σ of 1.0 is made transparent, 5 b-2 shows a ring-shaped maskelement on which a portion between IN σ of 0.4 and OUT σ of 1.0 is madetransparent, 5 b-3 shows a ring-shaped mask element on which a portionbetween IN σ of 0.2 and OUT σ of 1.0 is made transparent, 5 b-4 shows aring-shaped mask element on which a portion between IN σ of 0.4 and OUTσ of 0.8 is made transparent, 5 b-5 a ring-shaped mask element on whicha portion between IN σ of 0.2 and OUT σ of 0.8 is made transparent, 5b-6 a ring-shaped mask element on which a portion between IN σ of 0.4and OUT σ of 0.6 is made transparent, and 5 b-7 shows a ring-shaped maskelement on which a portion between IN σ of 0.2 and OUT σ of 0.6 is madetransparent. The ring-shaped mask elements 5 b-1 to 5 b-7 form thesecondary light source for the annular-looped illumination.

[0075] In FIGS. 4, 5b-8 shows a mask element which is formed with acircular transparent part for which the value σ is 0.89, 5 b-9 shows amask element which is formed with a circular transparent part for whichthe value a is 0.77, and 5 b-10 shows a mask element which is formedwith a circular transparent part for which the value σ is 0.65. Thesemask elements 5 b-8 to 5 b-10 form an ordinary secondary light sourcewith different values σ. The value σ of 1.0 indicates that it is equalto an aperture NA (Numerical Aperture): corresponding to the diameter ofthe pupil) of the objective lens 9.

[0076] FIGS. 5(a) and 5(b) are diagrams for showing practical dimensionsof the ring-shaped mask elements shown in FIG. 4, wherein M is a surfaceof an opaque mask which shuts off the light and shows IN σ and OUT σ.FIG. 5(b) shows the thickness t of the mask which is assumed as 2.3 mm.The diameters of OUT σ and IN σ of the ring-shaped mask elements of 5b-1 to 5 b-7 are shown in Table 1 below. TABLE 1 Part No. Diameter ofOUT σ Diameter of IN σ 5b-1 5.25 mm 3.15 mm 5b-2 5.25 mm 2.10 mm 5b-35.25 mm 1.05 mm 5b-4 4.20 mm 2.10 mm 5b-5 4.20 mm 1.05 mm 5b-6 3.15 mm2.10 mm 5b-7 3.15 mm 1.05 mm

[0077] The inside part of IN σ is made to be opaque in theabove-described ring-shaped mask elements. When it is made opaque, thelight quantity reduces and therefore the inside part of IN σ can be madeto be opaque to conform to the patterns on the high density inspectedobject 1 without substantially reducing the light quantity. The partbetween IN σ and OUT σ can be substantially transparent. Although, inthe above embodiment, the part between IN σ and OUT σ is formed with aring-shaped transparent member, it is obvious that the part can beformed by arranging a plurality of circular transparent members in theshape of ring.

[0078] As described above, many kinds of secondary or virtual lightsources can be formed by forming many types of mask elements on the disctype mask 5 and therefore an appropriate incident illumination light forvarious inspected objects 1 can be obtained. Consequently, the 0th orderdiffraction light and the first order diffraction light (+ first orderdiffraction light or − first order diffraction light) obtained fromvarious inspected objects 1 can be introduced into the opening (pupil)10 a of the objective lens 9 and two-dimensional image signals having asufficient resolution for various inspected objects 1 can be obtainedfrom the image sensor 12 a.

[0079] Two-dimensional image signals having a sufficient resolution fora high density pattern on the inspected object can be obtained by usingthe annular-looped illumination for the following reason. In case ofordinary illumination, the incident angle ψ of an incident illuminationlight 30 shown in FIG. 12 is approximately 0. In a case that the pitch Pof the inspected object 1 is small (in case of a high density pattern),the diffraction angle θ of the 0th order diffraction light (m=0) isequal to the incident angle ψ to be within the pupil 10 a of theobjective lens 9 for the relation represented by the equation 2.However, the diffraction angles θ of the + first order diffraction lightand the − first order diffraction light become large because theabove-described pitches P is small, and cannot therefore be introducedinto the pupil 10 a of the objective lens 9. Accordingly, only the 0thorder diffraction light, that is, the light of the DC component, isobtained from the high density pattern on the inspected object and theimage based on the diffraction light cannot be obtained from the patternon the inspected object.

[0080] The above relationship can be further described in detailaccording to the Abbe's diffraction theory. In other words, the Abbe'sdiffraction theory applies to the relationship between the incidentangle ψ to the optical axis of the incident illumination light 30 andthe space frequency to be focused.

[0081] Whether a grid pattern on the inspected object can be focuseddepends on whether the first order diffraction light from the gridpattern on the inspected object can pass through the pupil 10 a of theimaging system (objective lens 9). If the focusing point remains insidethe pupil 10 a when a diffraction light 31 is focused onto one point ofthe pupil 10 a of the imaging system (objective lens 9), the diffractionlight passes through the imaging system (objective lens 9) andinterferes with the 0th order diffraction light on the imaging plane toform the image of the grid pattern. This configuration is advantageousin that a focal depth can be larger.

[0082] When the structure of the grid pattern on the inspected object isfine (the pitch P becomes small), the angle θ of the first orderdiffraction light to the optical axis becomes large and, when the angleθ is larger than NA of the imaging system (objective lens 9), the firstorder diffraction light cannot pass through the pupil 10 a of theimaging system (objective lens 9) and the image of the grid pattern willnot be formed.

[0083] Although the resolution is improved in a plane between theoptical axis and the light source in a simple slanted illumination, theresolution is not improved in other planes. To improve the resolution inan optional direction, it is necessary to apply the annular-loopedillumination as described above and prevent an incident illuminationlight, the first order diffraction light of which is not introduced intoNA of the imaging system (objective lens 9) from being introduced inaccordance with the direction of the pattern on the inspected object.

[0084] A method of illumination in which the 0th order diffraction lightdoes not enter into the pupil 10 a of the imaging system (objective lend9) corresponds to the so-called dark field illumination. If there isonly the first order diffraction light in the opening of the imagingsystem (objective lens 9) with the dark field illumination as describedabove, the resolution is extremely low.

[0085] In FIG. 1, the CPU 20 controls the annular-looped illuminationaccording to the information detected by the image sensor 12 b, whichserves as a monitor for the pupil 10 a of the objective lens 9, bydriving the moving mechanism 19 to change over the light source for theannular-looped illumination comprising the disc type mask 5 (secondarylight source for annular-looped illumination) so that the first orderdiffraction light and the 0th order diffraction light always enter intothe pupil 10 a of the objective lens 9 even when the pattern of theinspected object 1 changes. Specifically, the CPU 20 uses the image ofthe Fourier transform plane (the surface of the pupil 10 a of theobjective lens 9) detected by the image sensor 12 b and controls theannular-looped illumination to shut off the incident illumination light,a first order diffraction light 23 of which does not enter into thepupil 10 a of the objective lens 9, or lowers the intensity of theincident illumination light in accordance with the pattern of theinspected object 1 by driving and controlling the moving mechanism 19 tochange over the disc type mask 5 to 5 a-1, 5 a-2, . . . , or 5 b-1, 5b-2, . . .

[0086] However, if the periodicity is not observed in the pattern of theinspected object, that is, in a case of a diffraction light (diffractioncomponents are continued) having various diffraction angles in a widespread, the pattern can be regarded as an isolated pattern (noperiodicity is observed) and therefore excessively slanted introductionof the incident illumination light is avoided and the illumination fromthe secondary light source for an appropriate annular-loopedillumination (mask elements 5 b-4, 5 b-5, 5 b-6 and 5 b-7 (with smallOUT σ) on the disc type mask 5 shown in FIG. 4) or the light source foran ordinary circular illumination (mask elements 5 b-8, 5 b-9 and 5b-10) is selected.

[0087] The edge detector 21 differentiates the image signals of thepattern of the inspected object 1 detected by the image sensor 12 a anddetects the edge information of the pattern of the inspected object 1through processing of the threshold value. Accordingly, the CPU 20calculates the width of the pattern of the inspected object 1 bycalculating, for example, an area surrounded by the edge of the patternaccording to the edge information of the inspected object 1 detected bythe edge detector 21, then calculates the density (pitch P) of thepattern of the inspected object 1 according to the pattern width of thisinspected object 1, and controls the annular-looped illumination bydriving and controlling the moving mechanism 19 and changing over thelight source for the annular-looped illumination which comprises thedisc type mask 5 in accordance with the calculated density (pitch P) ofthe pattern of the inspected object 1. For example, when the density ofthe pattern is high, the incident illumination light is introduced at amore slanted angle.

[0088] Specifically, the CPU 20 compares the density of the pattern ofthe inspected object 1 to be calculated with a preset value, controlsthe annular-looped illumination in accordance with the density of thepattern or selects the mask elements 5 b-1, 5 b-2 and 5 b-3 (with alarger OUT σ) shown in FIG. 4 as the light source for the annular-loopedillumination so that a slanted incident component is increased as thedensity of the pattern is higher.

[0089] The control of the annular-looped illumination by the CPU 20 canbe carried out under a predetermined or preset condition (information asto the type of the pattern of the inspected object 1 to be entered byinput unit 32 and mounted on the stage 2 or information as to the typeincluding the process of the inspected object 1 to be obtained from thehost computer which controls the manufacturing processes for theinspected object 1 and mounted on the stage 2). In other words, it isnecessary to control the annular-looped illumination so as to use theannular-looped illumination available under the preset condition (anannular-looped illumination approximate to a circular illumination (maskelements 5 b-4, 5 b-5, 5 b-6 and 5 b-7 (with a smaller OUT σ)) on thedisc type mask 5 shown in FIG. 4) or a circular illumination (maskelements 5 b-8, 5 b-9 and 5 b-10 shown in FIG. 4) since the density ofthe pattern is not so high and the pattern can be identified with a lowresolution in a case that the type of the inspected object 1 to bemounted on the stage 2 is, for example, a 4 Mb DRAM memory element, andto use the annular-looped illumination which provides a high resolutionunder the preset conditions (mask elements 5 b-1, 5 b-2, and 5 b-3 (witha larger OUT σ) shown in FIG. 4) since a high density pattern should bedetected with the high resolution in a case that the type of theinspected object 1 is the 16 Mb DRAM memory element.

[0090] If a mask element with the value σ of approximately 0.5 smallerthan that of the mask element 5 b-10 (σ is 0.65) shown in FIG. 4 is usedin the circular illumination, the image sensor 12 a receives an image ofa deep groove or hole and image signals with high contrast of a patternincluding deep grooves or holes can be obtained.

[0091] For example, the cell part of the memory element where thepattern density is high can be inspected with the annular-loopedillumination which provides a high resolution under the preset conditionand rough areas other than the cell part can be inspected with theordinary circular illumination so that the inspection sensitivity is notdeteriorated (so that the intensity of the incident illumination lightis not reduced).

[0092] Thus, various patterns (circuit patterns) can be detected withhigh resolution and sensitivity with the objective lens (imaging opticalsystem) 9 by using various modes of annular-looped illuminationsincluding the circular illumination and particularly, the annular-loopedillumination can apply to high density patterns on which the degree ofintegration is increased. The NA of the objective lens (imaging opticalsystem) 9 need not be larger than required so as not to suffice thefocal depth.

[0093] In a case that the first order diffraction light is preventedfrom entering into the pupil 10 a of the objective lens 9 by, forexample, the attenuation filter 38 for partly controlling the lightintensity provided at a position 10 b conjugated with the pupil 10 a ofthe objective lens 9, the 0th order diffraction light which reaches theattenuation filter 38 through the pupil 10 a of the objective lens 9 isshut off or the intensity of this diffraction light is reduced. In acase that the + first order, − first order and 0th order diffractionlights are introduced into the pupil 10 a of the objective lens 9, theintensities of the first order and 0th order diffraction lights arecontrolled to be coincided by, for example, the attenuation filter 38for partly controlling the light intensity.

[0094] The CPU 20 is able to partly control the transmissivity(attenuation ratio) by driving and controlling the moving mechanism 39and changing over the attenuation filter 38 according to the informationdetected by the image sensor 12 b, which serves a monitor for the pupil10 a of the objective lens 9, to make the image sensor 12 a balance andreceive the 0th order diffraction light and the first order diffractionlight in accordance with the pattern of the inspected object 1.

[0095] The detection of the grid pattern in the LSI wafer patterns asshown in FIG. 6 is now described as an example of the inspected object 1with high resolution by using the annular-looped illumination. FIG. 6 isa schematic diagram showing a grid pattern comprising lines and spacesin a peripheral circuit of the LSI wafer pattern. In FIG. 6, 101 is apattern line (a wiring pattern including a gate) which extends in the Yaxis direction. This grid type pattern line 101 is repeated at the pitchP in the X axis direction. A space (which may be formed with insulation)is formed between the pattern lines 101.

[0096]FIG. 7 is a schematic illustration showing, on the pupil 10 a ofthe objective lens 9, the incident annular-looped illumination 24 forilluminating the grid pattern shown in FIG. 6, and 0th order diffractionlight 22 a, + first order diffraction light 25 a and − first orderdiffraction light 26 b obtained from reflection of incident illuminationlight 24 a onto the X-Z plane passing through the optical axis 33 fromthe grid pattern shown in FIG. 6. FIG. 8 is a schematic illustrationshowing the 0th order diffraction light 22 a, the + first orderdiffraction light 25 a and − first order diffraction light 26 a obtainedon the X-Z plane passing through the optical axis 33 from reflection ofthe incident illumination light 24 a shown in FIG. 7 from the gridpattern shown in FIG. 6.

[0097] As shown in FIGS. 7 and 8, in the pupil 10 a of the objectivelens 9, the 0th order diffraction light 22 a and the + first orderdiffraction light 25 a are observed as having an area and as not beingpoints on an image detected by the image sensor 12 b which serves as themonitor for the pupil 10 a of the objective lens 9. Reference numeral 34denotes the range of the annular-looped illumination 24 on the gridpattern of th LSI wafer.

[0098] In a case that the grid pattern of the LSI wafer extends in the Yaxis direction as shown in FIG. 6, the incident angle ψ of the incidentillumination light 24 a and the emission angle θ of the 0th orderdiffraction light 22 a are equal for the relationship represented by theequation 2 described later and the 0th order diffraction light 22 a isgenerated at a position symmetrical to the incident illumination light24 a as shown in FIGS. 7 and 8, and the + first order diffraction light25 a and − first order diffraction light 26 b are generated at left andright positions for the relationship represented by the equation 2.Since the grid pattern of the LSI wafer extends in the Y axis direction,the + first order diffraction light 25 a and − first order diffractionlight 26 a are generated at left and right positions in the pupil butnot generated at upper and lower positions therein and are weak ifgenerated. However, as apparent from FIGS. 7 and 8, not only the 0thorder diffraction light 22 but the + first order light 25 or − firstorder diffraction light 26 can always be entered into the pupil 10 a ofthe objective lens 9 by using the annular-looped illumination 24, andthe image signals of the grid pattern of the LSI wafer can be detectedwith high resolution by the image sensor 12 a.

[0099]FIG. 9 is a schematic illustration showing, on the pupil 10 a ofthe objective lens 9, the incident annular-looped illumination 24 forilluminating the grid pattern shown in FIG. 6, and 0th order diffractionlight 22 b, + first order diffraction light 25 b and − first orderdiffraction light 26b obtained from reflection of incident illuminationlight 24 b onto the Y-Z plane passing through the optical axis 33 fromthe grid pattern shown in FIG. 6. In other words, since the grid patternof the LSI wafer extends in the Y axis direction, the incident angle ψof the incident illumination light 24 b and the emission angle θ of the0th order diffraction light 22 b are equal for the relationshiprepresented by the equation 2 described later and the 0th orderdiffraction light 22 b is generated at a position symmetrical to theincident illumination light 24 b, and the + first order diffractionlight 25 b and − first order diffraction light 26 b are introduced intothe pupil 10 a of the objective lens 9 as shown in FIG. 9.

[0100] However, since the grid pattern of the LSI wafer extends in the Yaxis direction, the + first order diffraction light 25 b and − firstorder diffraction light 26 b are weak even though these diffractionlights enter into the pupil 10 a of the objective lens 9 and do nottherefore make a great contribution to the resolution of the gridpattern of the LSI wafer, and the annular-looped illumination in the Yaxis direction can be eliminated by using the mask element 5 a-n shownin FIG. 3. Although the first order diffraction light 23 b becomesweaker than the 0th order diffraction light 22 b, the resolution of thegrid pattern of the LSI wafer does not deteriorate considerably eventhough the 0th order diffraction light 22 b is entered into the pupil 10a of the objective lens 9 and received by the image sensor 12 a, whenboth the + first order diffraction light 25 b and − first orderdiffraction light 26 b are entered into the pupil 10 a of the objectivelens 9 as shown in FIG. 9.

[0101]FIG. 10 is a schematic illustration showing, on the pupil 10 a ofthe objective lens 9, incident annular-looped illumination light 24′ forilluminating the grid pattern shown in FIG. 6, and 0th order diffractionlights 22 a′ and 22 b′, + first order diffraction lights 25 a′ and 25 b′and − first order diffraction lights 26 a′ and 26 b′ obtained fromreflection of incident illumination lights 24 a′ and 24 b′ on the X-Zand Y-Z planes passing through the optical axis 33 from the grid patternshown in FIG. 6, in a case that OUT σ and IN σ of the annular-loopedillumination are respectively made larger than those shown in FIGS. 7 to9 for the pupil 10 a (NA) of the objective lens 9.

[0102] In a case that OUT σ and IN σ of the annular-looped illuminationare respectively made larger than those shown in FIGS. 7 to 9 for thepupil 10 a (NA) of the objective lens 9 as shown in FIG. 10, the + firstorder diffraction lights 25 b′ and − first order diffraction lights 26b′ are not entered into the pupil 10 a and, when the 0th orderdiffraction light 22 b′ is received by the image sensor 12 a, theresolution for the grid pattern is deteriorated. Therefore the 0th orderdiffraction light 22 b′ faced in the Y axis direction can be preventedfrom being generated by using the mask element 5 a-n shown in FIG. 3 toeliminate the annular-looped illumination in the Y axis direction.

[0103] The 0th order diffraction light 22 b′ can be prevented from beingreceived by the image sensor 12 a by providing, for example, attenuationfilter 38 for partly controlling the same light intensity as the maskelement 5 a-n shown in FIG. 3 at a position 10 b in conjugation with theposition of the pupil 10 a of the objective lens 9 and shutting off the0th order diffraction light 22 b′ faced to the Y axis direction. Theconfiguration as described above enables detection of the grid patternwith high resolution by the image sensor 12 a even with theannular-looped illumination of which OUT σ and IN σ are respectively setto be large for the pupil 10 a (NA) of the objective lens 9.

[0104] Although, in the embodiment shown in FIG. 10, it is describedthat OUT σ and IN σ are respectively set to be larger than those shownin FIGS. 7 to 9 for the pupil 10 a (NA) of the objective lens 9, also ina case that the pupil 10 a (NA) of the objective lens 9 is set to besmaller than that shown in FIGS. 7 to 9 while retaining the sizes of OUTσ and IN σ the same as those in FIGS. 7 to 9, a state of generation ofthe diffraction light entered into the pupil 10 a (NA) of the objectivelens 9 is as shown in FIG. 10 and it is necessary to prevent the 0thorder diffraction light 22 b′ from being received by the image sensor 12a. In a case that the pitch P of the grid pattern is finer than thatshown in FIGS. 7 to 9 and the wavelength λ of the annular-loopedillumination light is longer than that shown in FIGS. 7 to 9, generationof the diffraction light entering into the pupil 10 a (NA) of theobjective lens 9 is as shown in the embodiment in FIG. 10, and it isnecessary to prevent the 0th order diffraction light 22 b′ from beingreceived by the image sensor 12 a as known from the relationshiprepresented by the equation 2 described later.

[0105] A diffraction phenomenon obtained from the grid pattern with theannular-looped illumination is now described in the relationship betweenthe value σ of an optional annular-looped illumination and the incidentangle ψ to the optical axis 33 being described with reference to FIGS.11 and 12. Specifically, FIG. 11 is an illustration showing therelationship between the value σ of the objective lens 9 to the opticalaxis 33 and the incident angle ψ of the incident illumination light 30irradiated onto the grid pattern surface of the inspected object 1 andFIG. 12 is an illustration showing the relationship between the incidentangle ψ and the emission angle (diffraction angle) θ of the diffractionlight 31.

[0106] In FIG. 11, the value σ of the annular-looped illumination lightincident into the pupil 10 a of the objective lens 9 and the incidentangle ψ of the incident illumination light irradiated onto the inspectedobject 1 are given by the equations shown below:

σ1:σ2=sin ψ1:sin ψ2

sin ψ2=(σ2/σ1)×sin ψ1

[0107] In this examination, the objective lens 9 for which chromaticaberration is compensated and magnification of ×40 and NA=0.8 are givenis used.

[0108] In this objective lens 9, the maximum incident angle satisfiesNA=sin ψ max=0.8 in case of σ=1.0. In otherwords, σ=1.0 indicates NA(opening) (emission pupil) of the objective lens 9.

sin ψ=(σ/1)×0.8=0.8σ

[0109] According to the above relationship, the incident angle ψ can beobtained from the relationship represented by equation 1.

ψ=sin−1(0.8σ)  (Equation 1)

[0110] The relationship between the incident angle ψ and the diffractionangle θ is described below.

[0111] In FIG. 12, the diffraction angle θ of the m-th order diffractionlight 31 has the relationship given by equation 2.

P=mλ/(sin ψ−sin θ)

sin θ=sin y−mλ/P

θ=asin(sin ψ−mλ/P))  (Equation 2)

[0112] where λ is a wavelength (μm) of the illumination light, θ is adiffraction angle (emission angle), P is a pattern pitch (μm) and m is ssequential number of the diffraction light. In the equation 2, “asin”denotes “arc sin”.

[0113] Theoretical values (incident angle ψ and diffraction angle θ) tothe value σ of the annular-looped illumination light when the wavelengthλ and the pattern pitch P of the inspected object are changed accordingto the above equations 1 and 2 are given by Tables 2, 3, 4 and 5 below.TABLE 2 λ = 0.4 μm P = 0.61 μm (256 Mb) σ 1.00 0.90 0.80 0.70 0.60 0.500.40 0.30 0.20 0.10 Incident angle ψ 53.13 46.05 39.79 34.06 28.69 23.5818.66 13.89 9.21 4.59 − first order — — — — — — 77.35 63.60 54.66 47.37diffraction light + first order 8.29 3.68 −0.90 −5.40 −10.13 −14.83−19.62 −24.57 −29.72 −35.15 diffraction light

[0114] TABLE 3 λ = 0.6 μm P = 0.61 μm (256 Mb) σ 1.00 0.90 0.80 0.700.60 0.50 0.40 0.30 0.20 0.10 Incident angle ψ 53.13 46.05 39.79 34.0628.69 23.58 18.66 13.89 9.21 4.59 − first order — — — — — — — — — —diffraction light + first order −10.58 −15.28 −20.10 −25.06 −30.24−35.70 −41.58 −48.04 −55.45 −64.64 diffraction light

[0115] TABLE 4 λ = 0.4 μm P = 0.7 μm (64 Mb) σ 1.00 0.90 0.80 0.70 0.600.50 0.40 0.30 0.20 0.10 Incident angle ψ 53.13 46.05 39.79 34.06 28.6923.58 18.66 13.89 9.21 4.59 − first order — — — — — — 77.35 63.60 54.6647.37 diffraction light + first order 13.21 8.54 3.93 −0.55 −5.27 −9.87−14.56 −19.36 −24.29 −29.43 diffraction light

[0116] TABLE 5 λ = 0.4 μm P = 0.7 μm (64 Mb) σ 1.00 0.90 0.80 0.70 0.600.50 0.40 0.30 0.20 0.10 Incident angle ψ 53.13 46.05 39.79 34.06 28.6923.58 18.66 13.89 9.21 4.59 − first order — — — — — — — — — 69.58diffraction light + first order −3.28 −7.88 −12.54 −17.29 −22.16 −27.20−32.49 −38.11 −44.20 −51.00 diffraction light

[0117] Table 2 shows the values in a case that the wavelength λ is 0.4μm and the pattern pitch P is 0.61 μm, Table 3 shows the values in acase that the wavelength λ is 0.6 μm and the pattern pitch P is 0.61 μm,Table 4 shows the values in a case that the wavelength λ is 0.4 μm andthe pattern pitch P is 0.7 μm, and Table 5 shows the values in a casethat the wavelength λ is 0.6 μm and the pattern pitch P is 0.7 μm, andthe incident angle ψ and the diffraction angle θ are calculatedaccording to the above equations 1 and 2. In the LSI wafer pattern, thepattern pitch P=0.61 μm corresponds to 256 Mb and the pattern pitchP=0.7 μm corresponds to 64 Mb. In the above tables, “−” denotes thatcalculation is impossible (the − first order diffraction light is nottheoretically generated). If the diffraction angle θ of the first orderdiffraction light is 53.13 degrees or over, the first order diffractionlight does not enter into the pupil 10 a of the objective lens 9 ofNA=0.8.

[0118] A relationship between the annular-looped illumination (valueσ=0.4, 0.6) available with the above theoretical values and the + firstorder diffraction lights 25 and 25″ which are intensified and thenobtained from the grid pattern (FIG. 13 shows the pattern pitch P of0.61 μm and FIG. 14 shows the pattern pitch P of 0.7 μm) is shown inFIGS. 13 and 14 respectively.

[0119]FIG. 13(a) shows the + first order diffraction light 25 which isintensified by the annular-looped illumination 24 of value σ=0.4, 0.6(wavelength λ shall be within the range of 0.4 to 0.6 μm) and obtainedfrom the grid pattern (corresponding to 256 Mb in the LSI wafer pattern)with the pattern pitch P of 0.61 μm, and FIG. 13(b) is a diagram showingthe range of the incident angle ψ of the annular-looped illumination 24with the value σ of 0.4, 0.6 (wavelength λ shall be within the range of0.4 to 0.6 μm) and the diffraction angle θ of the + first orderdiffraction light obtained from the grid pattern (corresponding to 256Mb in the LSI wafer pattern) with the pattern pitch P of 0.61 μm.

[0120] The diffraction range (range of diffraction angle θ) of the +first order diffraction light shown in FIG. 13(b) corresponds to theannular-looped illumination with the value σ of 0.4, 0.6 in Tables 2 and3. Intersecting oblique lines in FIG. 13(b) shows the area of the +first order diffraction light (corresponding to the area of the + firstorder diffraction light in a case that the average wavelength(wavelength λ is 0.5 μm) of the annular-looped illumination light) whichis obtained from the grid pattern with the pattern pitch P of 0.61 μm bybeing intensified with the annular-looped illumination with the value σof 0.4, 0.6. In other words, FIG. 13(a) shows an annular-looped area 25of the + first order diffraction light which is intensified and obtainedfrom the grid pattern with the pattern pitch P of 0.61 μm and enteredonto the pupil 10 a of the objective lens 9.

[0121]FIG. 14(a) shows the + first order diffraction light 25″ which isintensified by the annular-looped illumination 24 with the value σ of0.4, 0.6 (wavelength λ shall be within the range of 0.4 to 0.6 μm) andobtained from the grid pattern (corresponding to 64 Mb in the LSI waferpattern) with the pattern pitch P of 0.7 μm, and FIG. 14(b) is a diagramshowing the range of the incident angle ψ of the annular-loopedillumination 24 with the value σ of 0.4, 0.6 (wavelength λ shall bewithin the range of 0.4 to 0.6 μm) and the diffraction angle θ of the +first order diffraction light obtained from the grid pattern(corresponding to 64 Mb in the LSI wafer pattern) with the pattern pitchP of 0.7 μm.

[0122] The diffraction range (range of diffraction angle θ) of the +first order diffraction light shown in FIG. 14(b) corresponds to theannular-looped illumination with the value σ of 0.4, 0.6 in Tables 4 and5. Intersecting oblique lines in FIG. 14(b) shows the area of the +first order diffraction light (corresponding to the area of the + firstorder diffraction light in a case that the average wavelength(wavelength λ is 0.5 μm) of the annular-looped illumination light) whichis obtained from the grid pattern with the pattern pitch P of 0.7 μm bybeing intensified with the annular-looped illumination with the value σof 0.4, 0.6. In other words, FIG. 14(a) shows an annular-looped area 25″of the + first order diffraction light which is intensified and obtainedfrom the grid pattern with the pattern pitch P of 0.7 μm and enteredonto the pupil 10 a of the objective lens 9.

[0123] From comparison of FIGS. 13 and 14, it is apparent that, if thepattern pitch P is smaller, the diffraction angle θ of the first orderdiffraction light becomes large and therefore the annular-loopedillumination is required.

[0124] Thus, the annular-looped illumination with the value σ of 0.4,0.6 as shown in FIGS. 13 and 14 can be materialized by using the maskelement 5 b-6 shown in FIG. 4.

[0125] The above description is based on the equations 1 and 2 shownabove. In an experiment conducted by the present inventors,substantially the same results were obtained (the result shown in FIG.13: the grid pattern with the pattern pitch P of 0.61 μm (correspondingto 256 Mb in the LSI wafer pattern); the result shown in FIG. 14: thegrid pattern with the pattern pitch P of 0.7 μm) (corresponding to 64 Mbin the LSI wafer pattern).

[0126] In the above-described embodiments shown in FIGS. 7 to 14, thegrid patterns which are repeated in the X axis direction in the LSIwafer pattern as shown in FIG. 6 have been described. Actually, in theLSI wafer pattern, there is a grid pattern comprising pattern lines 102to be repeated in the Y axis direction as shown in FIG. 15.

[0127] The diffraction lights 22 a, 25 a and 26 a obtained from the gridpattern comprising pattern lines 102 repeated in the Y axis direction asshown in FIG. 15 with the annular-looped illumination 24 are enteredinto the pupil 10 a of the objective lens 9 as shown in FIG. 16. Thegrid pattern comprising pattern lines 101 shown in FIG. 6 and the gridpattern comprising pattern lines 102 shown in FIG. 15 are shifted by 90degrees from each other and therefore the state shown in FIG. 16 isobtained by rotating the state shown in FIG. 7 by 90 degrees.

[0128] Accordingly, the state of generation of the diffraction lightobtained from the grid pattern comprising the pattern lines 102 shown inFIG. 15 is the same as obtained by rotating the state of generation ofthe diffraction light shown in FIGS. 8 to 10 by 90 degrees. In otherwords, it is apparent that the 0th order diffraction light 22 a, + firstorder diffraction light 25 a and − first order diffraction light 26 aobtained reflected at the grid pattern shown in FIG. 15 from theincident illumination light 24 a entered into the Y-Z plane passingthrough the optical axis 33 of the incident annular-looped illuminationlight 24, are made incident onto the pupil 10 a of the objective lens 9as shown in FIG. 16 and the incident illumination light 24 a in adirection intersecting the pattern lines 102 is effective forimprovement of the resolution.

[0129] However, even though the + first order diffraction light 25 b and− first order diffraction light 26 b, which are obtained from reflectionof the incident illumination light, which is made incident into the X-Zplane passing through the optical axis 33, of the incidentannular-looped illumination light 24 from the grid pattern shown in FIG.15, are introduced into the pupil 10 a of the objective lens 9 asdescribed in FIG. 9, such diffraction lights are weaker than the 0thorder diffraction light 22 b and do not contribute to improvement of theresolution and therefore it is preferable to eliminate the incidentillumination light to be made incident in the X axis direction (X-Zplane passing through the optical axis 33) of the incidentannular-looped illumination light 24 by using the mask element 5 a-mshown in FIG. 3.

[0130] In any event, the CPU 20 can detect the distribution of theincident diffraction light which is produced from the grid pattern andentered into the pupil 10 a of the objective lens 9 by theannular-looped illumination, according to the image signals obtainedfrom the image sensor 12 b which receives the image (the producingposition and brightness of the 0th order diffraction light 22 a and theproducing position and brightness of the + first order diffraction light25 a) on the pupil 10 a (Fourier transform plane) of the objective lens9.

[0131] In other words, the CPU 20 can select the mask element by drivingand controlling the moving mechanism 19 in accordance with thedistribution (the producing position and brightness of the 0th orderdiffraction light and the producing position and brightness of the +first order diffraction light 25 a) of the diffraction light to beentered into the pupil 10 a of the objective lens 9 detected accordingto the image signals to be obtained from the image sensor 12 b, and canobtain an annular-looped illumination suitable for the grid pattern (LSIwafer pattern) of the inspected object 1. Consequently, high resolutionimage signals of the grid pattern (LSI wafer pattern) of the inspectedobject 1 can be obtained from the image sensor 12 a.

[0132] The following describes the operation of a device as represented,for example, by the attenuation filter 38 for partly controlling theintensity of light which is provided at a position 10 b in conjunctionwith the position of the pupil 10 a of the objective lens 9.Specifically, as shown in FIGS. 9 and 10, the 0th order diffractionlight 22 b, 22 b′ which need not be entered into the pupil 10 a of theobjective lens 9 and received by the image sensor 12 a can be shut offby the attenuation filter 38. In this case, the attenuation filter 38serves as a space filter.

[0133] By controlling the intensity of the 0th order diffraction light22 a entered into the pupil 10 a of the objective lens 9 as shown inFIGS. 8 and 16 by the attenuation filter 38 provided at the position 10b in conjunction with the position of the pupil 10 a of the objectivelens 9 as shown in FIGS. 17 and 18, the image sensor 12 a is able tobalance the intensity of the 0th order diffraction light 22 a and theintensity of the + first order diffraction light 25 a which are enteredinto the pupil 10 a of the objective lens 9 and receive thesediffraction lights and consequently, the image of the grid pattern ofthe inspected object 1 can be detected with high resolution and highcontrast. The above-described attenuation filter 38 has a shapeidentical to the mask element shown in FIG. 3. However, as shown in FIG.3, the attenuation filter 38 need not have a ring type shape and can beshaped as desired if it is able to control the light intensity at adesired position. However, if a ring-shaped attenuation filter 38 isused, it is necessary to optimize the annular-looped illumination 24 sothat the 0th order diffraction light 22 a and the + first orderdiffraction light 25 a are not generated in the same ring-shaped area.

[0134]FIG. 17 is a diagram showing that the 0th order diffraction light22 a and the + first order diffraction light 25 a generated from thegrid pattern of the inspected object 1 by the annular-loopedillumination 24 a reaches the pupil 10 a of the objective lens 9 and thepupil 10 b at a position in conjugation with the pupil 10 a. FIG. 18 isa diagram showing the attenuation filter 38 disposed on the pupil 10 b.In other words, it is known that, of the 0th order diffraction light 22a and the + first order diffraction light 25 a which are introduced intothe pupil 10 a of the objective lens 9, the intensity of the 0th orderdiffraction light 22 a is controlled on the pupil 10 a by theattenuation filter 38.

[0135]FIG. 19(a) is a schematic diagram of an attenuation filter 38 ashowing the transmission characteristic of the attenuation filter 38 aand FIG. 19(b) shows a graphical shape thereof. FIG. 20(a) shows anotherattenuation filter 38 b and the transmission characteristic thereof andFIG. 20(b) shows a graphical shape thereof. The transmissioncharacteristic of the attenuation filter 38 and the graphical shapethereof can be optimized in compliance with the 0th order diffractionlight 22 a and the + first order diffraction light 25 a which areproduced from the grid pattern of the inspected object 1 by theannular-looped illumination 24 a.

[0136] If the annular-looped illumination can be optimized in accordancewith the grid pattern (LSI wafer pattern) of the inspected object 1, theattenuation filter 38 need not be provided. However, for optimizationonly with the annular-looped illumination, it is necessary to prepareand select various types of annular-looped illuminations to meet varioustypes of patterns on the inspected object 1. For minimizing the scope ofselection of the annular-looped illumination, it is preferable tocontrol the intensities of the diffraction lights by using theattenuation filter 38 at the light receiving side and detect the imageof the grid pattern of the inspected object 1 in high resolution andcontrast by the image sensor 12 a.

[0137] The CPU 20 can select the attenuation filter 38 by driving andcontrolling the moving mechanism 39 in accordance with the distributionsof the diffraction lights (the producing position and brightness of the0th order diffraction light 22 a and the producing position andbrightness of the + first order diffraction light 25 a) which aredetected according to the image signals obtained from the image sensor12 b and entered into the pupil 10 a of the objective lens 9, and canobtain the intensities of the 0th order diffraction light and the +first order diffraction light suited to the grid pattern (LSI waferpattern) of the inspected object 1. Consequently, high resolution imagesignals of the grid pattern (LSI wafer pattern) of the inspected object1 can be obtained from the image sensor 12 a.

[0138] Since it is difficult to implement optimization only with ehannular-looped illumination to meet various patterns on eh inspectedobject 1, it is necessary to control the intensities of the diffractionlights received by the image sensor 12 a through the attenuation filter38 as described above, and the detection sensitivity by controlling thethreshold values in image processing to be carried out by the comparatorcircuit 17 or the CPU 20. The control of the threshold values in imageprocessing to be carried out by the comparator circuit 17 or the CPU 20can be carried out according to the image on the pupil 10 b of theobjective lens 9 to be detected by the image sensor 12 b or the image ofthe pattern on the inspected object 1 to be detected by the image sensor12 a.

[0139] The CPU 20 can be adapted to determine an area having a patternwith high repeatability such as, for example, a memory cell inaccordance with a locality distribution (the producing position and theintensity including the spread) of the diffraction light in the image(image on the pupil 10 b of the objective lens 9) on the Fouriertransform plane to be detected by the image sensor 12 b, and to controlthe threshold values in image processing to be carried out by thecomparator circuit 17 or the CPU 20, to raise the detection sensitivity.On the contrary, in a case that the CPU 20 determines an area having apattern with a lower repeatability, the detection sensitivity can belowered by controlling the threshold values in image processing to becarried out by the comparator circuit 17 or the CPU 20.

[0140] Particularly, for inspecting a defect of a pattern on theinspected object 1 in image processing to be carried out by thecomparator circuit 17 or the CPU 20, a defect in an area including apattern having high repeatability such as, for example, a memory cellcan be easily detected with the annular-looped illumination, bycontrolling the threshold values to increase the detection sensitivityin accordance with the locality distribution (the producing position andthe intensity including the spread) of the diffraction light in theimage (the image on the pupil 10 b of the objective lens 9) on theFourier transform plane to be detected by the image sensor 12 b.

[0141] Another embodiment in which the shape of the ring of theannular-looped illumination to be emitted from the disc type mask(secondary light source for annular-looped illumination) formed with aplurality of virtual spot light sources is changed is described withreference to FIGS. 21 and 22. In other words, FIGS. 21 and 22 show otherembodiments for controlling various annular-looped illuminations. InFIG. 21, the shape of the ring is changed and the annular-loopedillumination is controlled by moving the light house 124 comprising theXe lamp 3, the elliptic mirror 4 and the disc type mask 5 for formingthe annular-looped illumination towards the collimator lens 6 in theoptical axis direction. In FIG. 22, the shape of the ring is changed andthe annular-looped illumination is controlled by moving the collimatorlens 6 toward the light house 124 comprising the Xe lamp 3, the ellipticmirror 4 and the disc type mask 5 for forming the annular-loopedillumination in the optical axis direction.

[0142] In an embodiment of the light house 124 which forms the secondarylight source 5 for the annular-looped illumination formed with aplurality of virtual spot light sources shown in FIGS. 1, 21 and 22, anarrangement of the Xe lamp 3 in the vertical direction is shown. Whenthe Xe lamp 3 is arranged in the vertical direction, the light flux inthe optical axis direction reduces and therefore the Xe lamp can bearranged in the horizontal direction to increase the light flux in theoptical axis direction. Not only the Xe lamp but also a Hg lamp and ahalogen lamp can be used as the light source in the light house 124.

[0143] In a case that the disc type mask 5 (secondary light source forannular-looped illumination) formed with a plurality of virtual spotlight sources is selected in accordance with the pattern of theinspected object 1, the light quantity of the annular-loopedillumination emitted from the secondary light source 5 for theannular-looped illumination substantially varies and the CPU 20 controlsthe light quantity by controlling the light quantity adjusting filter 14such as an ND filter in accordance with an image signal 41 obtained fromthe image sensor 12 a through the A/D converter 19.

[0144] A microscope system (microscopic observation system) to be usedin inspection of a pattern of an inspected object 1 using anannular-looped illumination according to the present invention isdescribed with reference to FIG. 23 which shows a microscope system(microscopic observation system) according to a second embodiment of thepresent invention applied to the inspection of the pattern of theinspected object 1 such as an LSI wafer pattern (microscopic observationsystem) according to the second embodiment of the present invention.

[0145] The microscope system using the annular-looped illuminationformed with a plurality of virtual spot light sources is described onlywith respect to its characteristic parts with omission of thedescription of the parts common to the pattern inspection apparatusshown in FIG. 1. In FIG. 23, members 12 a′ and 12 b′ represent TVcameras which are used as the image sensors 12 a and 12 b shown in FIG.1 and the operator can visually observe the output images from the TVcameras on monitors 27 a and 27 b. Members 12 a′ and 12 b′ can be usedif they can detect the image, and can therefore be formed with imagesensors and not the TV cameras.

[0146] In other words, the TV camera 12 a′ detects a pattern image andthe TV camera 12 b′ detects an image on a pupil 10 a of an objectivelens 9, and these images are displayed on the monitors 27 a and 27 b. Acontroller 46 is connected to a specimen stage 2 so as to be driven andcontrolled for movement in X, Y, Z and θ (rotation) axis directions by adriver 45. This controller 46 drives and controls the moving mechanism19, the light house 124, and the collimator lens 6 in accordance with animage with a locality distribution of the first order diffraction lightincluding the 0th order diffraction light which are introduced into thepupil 10 a of the objective lens 9 and detected by the TV camera 12 b′and displayed on the monitor 27 b, and selects the annular-loopedillumination or a normal circular illumination suited for the pattern ofthe inspected object 1. For driving and controlling the disc type mask 5by the moving mechanism 19, a mask element formed on the disc type mask5 can be selected. For driving and controlling the light house 124 andthe collimator lens 6, these can be driven and controlled relatively inthe arrow direction as shown in FIGS. 21 and 22.

[0147] The controller 46 drives and controls the moving mechanism 39 andselects an attenuation filter 38 suited for the pattern of the inspectedobject 1 according to an image of a locality distribution of the firstorder diffraction light including the 0th order diffraction light whichare entered into the pupil 10 a of the objective lens 9 and detected bythe TV camera 12 b′ displayed on the monitor 27 b. If a circularillumination suitable or normal for the pattern of the inspected object1 can be selected with the secondary light source 5 for theannular-looped illumination, the attenuation filter 38 need not alwaysbe provided.

[0148] The controller 46 controls the light quantity control filter 14to obtain an appropriate quantity of light from the pattern of theinspected object 1 by driving and controlling a control mechanism 14 baccording to an image of the pattern of the inspected object 1 which isdetected by the TV camera 12 a′ and displayed on the monitor 27 a.

[0149] A microscopic observation system thus using the annular-loopedillumination enables to observe a high density pattern with highresolution and contrast according to the image of the pattern of theinspected object 1, which is detected by the TV camera 12 a′ anddisplayed on the monitor 27 a, even though the pitch P (for example, 0.7μm or 0.61 μm) of the grid pattern such as memory devices as 64 Mb DRAMand 256 Mb DRAM as on the LSI wafer pattern is close to wavelength λ(for example, 400 to 600 nm) of the illumination light to result in thehigh density.

[0150] When a mask element with the value σ of approximately 0.5 is usedfor illumination in the annular-looped illumination, an image of deepgroove or hole can be received by the TV camera 12 a′ and displayed withhigh contrast on the monitor 27 a.

[0151] Modifications of the above-described first and second embodimentsas a third embodiment are now described. The above-described first andsecond embodiments have been described with respect to theannular-looped illumination and the circular illumination. Theabove-described annular-looped illumination includes a modifiedillumination (slanted illumination) (This modified illumination is basedon the illuminating condition under which at least the 0th orderdiffraction light and the first order or second order diffraction lightare introduced into the pupil 10 a of the objective lens 9.). The darkfield illumination is not included in the modified illumination (slantedillumination) since the 0th order diffraction light thereof is notgenerally entered into the pupil 10 a of the objective lens 9.

[0152] In the first and second embodiments, the transmissivity of lightis attenuated by the attenuation filter 38 as shown in FIGS. 19 and 20.However, the light quantity of the 0th order diffraction light 22 a canbe attenuated as compared with the + first order diffraction light 25 areceived by the image sensor 12 a by a phase shifting method, that is, amethod for shifting the phase of the 0th order diffraction light 22 a byusing a phase film. In other words, although a device such as theattenuation filter 38 for partly controlling the light intensity isprovided at a position 10 b in conjugation with the position of thepupil 10 a of the objective lens 9 in the first and second embodiments,a phase plate can be provided at this position 10 b. For example, theintensity of the 0th order diffraction light 22 a received by the imagesensor 12 b can be attenuated by advancing the phase of the 0th orderdiffraction light 22 a as much as π/2 with reference to the phase ofthe + first order diffraction light 25 a. In addition, the intensity ofthe 0th order diffraction light 22 a to be received by the image sensor12 b can be attenuated by providing the phase plate with an absorptioncharacteristic.

[0153] Although, in the first and second embodiments, the 0th orderdiffraction light and ± first order diffraction lights are described ina combination framework, it is apparent that these embodiments can applyto the framework of the 0th order diffraction light (non-diffractionlight) and the diffraction light (± first order diffraction lights and ±second order diffraction lights). In other words, the annular-loopedillumination can be used so that the 0th order diffraction light andthe + second order diffraction light or − second order diffraction lightobtained from the pattern are made incident into the pupil 10 a of theobjective lens 9, even though the pitch P of the pattern becomes finer(the pattern has a higher density). Generally, the first orderdiffraction angle is smaller than the second order diffraction angle asgiven in the relationship represented by the equation 2. However, insome cases, the second order diffraction angle may be smaller than thefirst order diffraction angle depending on the pitch P of the patternand the wavelength λ of the annular-looped illumination.

[0154] In the first and second embodiments, for example, the Xe lamp 3(the dimensions are not shown) is used as the light source in the lighthouse 124 but a large light source (a light source which irradiates anincoherent light) or a spot light source (a light source whichirradiates a coherent light) can be used. An appropriate value σ can beobtained only with the primary light source (without a mask element) byselecting the light source.

[0155] Although the first and second embodiments are described with acommon wavelength of 400 to 600 nm as the wavelength λ of theannular-looped illumination, the illumination wavelength is notdescribed. A wavelength of the so-called i ray (approximately 365 nm) ora short wavelength of an excimer laser beam (ultraviolet ray) can beused as the wavelength λ of the annular-looped illumination. It isapparent that the resolution can be further improved if a light of shortwavelength such as the excimer laser beam (ultraviolet ray) is used.

[0156] The control of the annular-looped illumination in the first andsecond embodiments can be carried out for each type of pattern of theinspected object (for example, in case of the LSI wafer pattern, eachprocess or each type of the LSI wafer). The annular-looped illuminationcan be dynamically controlled in one LSI wafer. In case of inspecting adefect of the pattern of the inspected object 1, the sensitivity can becontrolled for each type of pattern of the inspected object as in thecontrol of the annular-looped illumination or can be dynamicallycontrolled in one LSI wafer.

[0157] The secondary light source for the annular-looped illumination,including the primary light source (Xe lamp 3) for use in the lighthouse 124 in the first and second embodiments can be adjusted by using amirror surface wafer as the inspected object 1 so that a ring typeintensity distribution (a distribution of a ring-shaped 0th orderdiffraction light 22 on the pupil 10 a of the objective lens 9 to bedetected by the image sensor 12 b) becomes uniform. In other words, thesecondary light source for the annular-looped illumination can beadjusted by adjusting, for example, the positions of the Xe lamp 3 andan elliptic mirror 4 which forms the secondary light source for theannular-looped illumination so that the distribution of the ring-shaped0th order diffraction light 22 on the pupil 10 a of the objective lens 9detected by the image sensor 12 b using the mirror surface wafer as theinspected object 1.

[0158] In the first and second embodiments, it is described that theimage information (monitor information) based on the localitydistribution (position and brightness, including the spread) of thediffraction lights (0th order diffraction light and + first orderdiffraction light) on the pupil 10 a of the objective lens 9 detected bythe image sensors 12 b and 12 b′ is used to control various parts by theCPU 20 or the controller 46. In other words, the control of theconditions for various parts includes the control of illuminationconditions such as control of the annular-looped illumination (forexample, control of IN σ and OUT σ and the incident range shown in FIGS.3 and 4) and the light quantity control by means of the light quantitycontrol filter 14, the control of the light quantity detected by theattenuation filter 38, and the control of detection sensitivity in thecomparator circuit 17. The CPU 20 or the controller 46 determineswhether the image information based on the locality distribution of thediffraction lights on the pupil 10 a of the objective lens 9 detected bythe image sensors 12 b and 12 b′ is obtained, for example, from therepeated portion or the other area of the memory device andconsequently, can controls the annular-looped illumination including anappropriate circular illumination in accordance with whether theidentified repeated portion or the other portion.

[0159] A fourth embodiment of the present invention for inspecting adefect of a memory cell part of an LSI wafer pattern by using anannular-looped illumination to improve the optical resolution isdescribed with reference to FIGS. 24 to 27. FIG. 24 shows a defect ofthe memory cell part of the LSI wafer pattern. FIG. 25 shows therelationship between the LSI wafer pattern and the detection pixelobtained from an A/D converter 15 a. FIGS. 26(a) and 26(b) show apattern and a waveform of an image signal received with high resolutionfrom a high density pattern by the image sensor 12 a with theannular-looped illumination and obtained from the image sensor 12 a.FIGS. 27(a) and 27(b) explain sampling of image signals shown in FIG. 26to be carried out by the A/D converter 15 a.

[0160] There are various defects (for example, a projection 231, anopening 232, a discoloration 233, a short-circuiting 234, a chipping235, and a stain 236) on the memory cell part of the LSI wafer patternas shown in FIG. 24 and therefore, for detecting these defects with highreliability, the inspection apparatus should be able to detect the LSIwafer pattern as image signals with high resolution by the image sensor12 a. High resolution image signals shown in FIG. 26(b) are obtainedfrom the pattern shown in FIG. 26(a) by using the annular-loopedillumination. FIG. 26(a) shows a partly extended view of the patternshown in FIG. 24 and FIG. 26(b) shows the waveform indicating theposition of the pattern A-A′ on the horizontal axis and the brightnessof the image signal (pattern detection signal) obtained from the imagesensor on the vertical axis. In FIG. 26(a), it is shown that highresolution image signals representing the edge information of thepattern are obtained from the image sensor 12 a by using theannular-looped illumination.

[0161] When the annular-looped illumination is used, the + first orderdiffraction light with various diffraction angles and a spread (dullspread) is obtained from the defects such as the projection 231, thechipping 236 and the stain 235 and image signals differing from thepattern can be obtained from the image sensor 12 a. When theannular-looped illumination is used, the image signals including thoseof the opening 232 and the short-circuiting 234, differing from thepattern can be obtained from the image sensor 12 a since the + firstorder diffraction light component in the X axis direction is notgenerated. When the annular-looped illumination is used, generation of,for example, the 0th order diffraction light from the discolorationdefect 233 differs from that from an area where there is nodiscoloration defect, and the image signal showing the discolorationdefect 233 can be obtained from the image sensor 12 a.

[0162]FIG. 25 shows a case that the detection pixel to be sampled in theA/D converter 15 a with respect to the LSI wafer pattern shown in FIG.24 is large. In the case that the detection pixel 241 to be sampled inthe A/D converter 15 a is large as shown in FIG. 25, two edges of thepattern remain in one detection pixel 241 and the edge information ofthe pattern will be lost.

[0163] To prevent loss of the edge information of the pattern, thedimensions of the detection pixel 241 to be sampled in the A/D converter15 a can be reduced. When the dimensions of the detection pixel arereduced, sampled digital image signal information obtained from the A/Dconverter 15 a increases, a volume of defect detection image signalinformation to be processed in the comparator circuit 17 also increasesand therefore it takes a lot of time to detect the defect. Accordingly,as shown in FIG. 27, the pattern A-A′ can be sampled in a detectionpixel size that the minimum and maximum values of brightness of thepattern are preserved, and converted to the digital image signalsshowing the shad (brightness).

[0164] The CPU 20 calculates an interval between the minimum value (edgeinformation of the pattern) and the maximum value of the brightness ofthe pattern from a digital image signal 41 (shown in FIG. 27(a))obtained from the A/D converter 15 a by reducing the pixel size to besampled by the A/D converter 15 a, and sets a detection pixel size bywhich these minimum and maximum values can be divided. The A/D converter15 a carries out sampling according to the detection pixel size 42 setin the CPU 20 and therefore the digital image signal (shown in FIG.27(b)) showing the shade (brightness) which is sampled in a relativelylarge detection pixel size can be obtained without losing the edgeinformation of the pattern. Consequently, the volume of information forprocessing the defect detection image to be carried out in thecomparator circuit 17 and others can be reduced and the defect can bedetected in high speed and reliability.

[0165] Referring to FIG. 27(a), the CPU 20 sets the pixel size to besampled to be small for the A/D converter 15 a, selects X1/2 as thedetection pixel size among X1, X2, X3 and X4 portions which have therelation of X1=X2=X3=X4 from the digital image signal 41 obtained fromthe A/D converter 15 a, and sets X5 and X6 portions where the intervalbetween the minimum value and the maximum value is large so that thedetection pixel size is 3X₁/2 and 2X₁. A signal 42 corresponding to thedetection pixel size which is set as described above is supplied to theA/D converter 15 a.

[0166]FIG. 27(b) shows a waveform of a digital image signal sampled inthe A/D converter 15 a according to the signal 42 supplied from the CPU20 for the waveform of the image signal of A-A′ part shown in FIG.27(a). As known from FIG. 27(b), in the A/D converter 15 a, the digitalimage signals which contain the minimum and maximum values showing thepattern edge are obtained from the image signals outputted from theimage sensor 12 a. With this, the image signals showing the pattern edgeto be obtained in high resolution are erased and a defect can beinspected with high reliability at a high speed by cell-comparing orchip-comparing digital image signals which are delayed as far as thecell interval or the chip interval in the delay memory 16 and thedigital image signals directly obtained from the A/D converter 15 a. Theimage signals indicating the pattern edge are repeated at the cellinterval or the chip interval and simultaneously detected in cellcomparison or chip comparison in the comparator circuit 17 and the imagesignal indicating the pattern edge can be erased. Consequently, a signal18 indicating a defect can be detected unmatched in cell or chipcomparison in the comparator circuit 17.

[0167] The CPU 20 can set the detection pixel size to X=X₁/4 or X₁/8 tocarry out sampling of digital image signals between the minimum valueand the maximum value. Thus, the A/D converter 15 a can obtain thedigital image signals showing the shade (brightness) from sampling inthe above set detection pixel size (X=X₁/4 or X₁/8). In this case, thesampling interval is reduced and therefore high resolution image signalsobtained from the image sensor 12 a can be faithfully converted to thedigital image signals.

[0168] The CPU 20 can vary the magnification of the image received bythe image sensor 12 a according to the digital image signal 41, which isobtained from the A/D converter 15 a by reducing the pixel size to besampled for the A/D converter 15 a, by controlling the zoom lens 13 witha zoom lens control signal 43 as shown in FIG. 1. Consequently, eventhough the signal 42 for determining the detection pixel size is fixedin the A/D converter 15 a, the detection pixel size to be sampled can bevaried in accordance with the magnification depending on the zoom lens13. Accordingly, for varying the magnification depending on the zoomlens 13, the zoom lens can be controlled with a command from the CPU 20.

[0169] In addition, sampling of high resolution image signals obtainedby receiving the 0th order diffraction light 22 a and the + first orderdiffraction light 25 a, which are generated from the grid pattern by theannular-looped illumination and entered into the pupil 10 a of theobjective lens 9, in the A/D converter 15 a is described with referenceto FIGS. 28, 29 and 30. The grid pattern (wafer pattern formed withlines and spaces) respectively shown in FIGS. 28(a) to 30(a) is arepetitive pattern comprising lines of 0.42 μm in width and spaces of0.42 μm in width which are repeated at the pitch P of 0.84 μm.

[0170] The waveform of the sampled digital image signal showing theshade (brightness) shown in FIG. 28(b) is obtained when the detectionpixel size is set to 0.0175 μm and it is known that the edge informationof the grid pattern is clearly detected. In other words, it is indicatedthat high resolution image signals obtained by being received by theimage sensor 12 a are faithfully converted to the digital image signalindicating the shade (brightness) by the A/D converter 15 a.

[0171] The waveform of the sampled digital image signal showing theshade (brightness) shown in FIG. 29(b) is obtained when the detectionpixel size is set to 0.14 μm and it is known that the edge information(information of ultimate values such as minimum and maximum values) ofthe grid pattern is detected as being stored.

[0172] The waveform of the sampled digital image signal showing theshade (brightness) shown in FIG. 30(b) is obtained when the detectionpixel size is set to 0.28 μm and it is known that the edge information(information of ultimate values such as minimum and maximum values) ofthe grid pattern is detected as being partly missed.

[0173] Therefore, the repetitive pattern (grid pattern) comprising linesof 0.42 μm in width and spaces of 0.42 μm in width which are repeated atthe pitch P of 0.84 μm should be converted to the digital image signalindicating the shade (brightness) by sampling in the A/D converter 15 awhile setting the detection pixel size to be set according to the signal42 from the CPU 20 to approximately 0.3 μm or less. With this, the edgeinformation (information of ultimate values such as minimum and maximumvalues) of the grid pattern is detected as being stored in the digitalimage signal showing the shade (brightness) and can be detected as beingdiscriminated from the defect and therefore those defects (projection231, opening 232, discoloration 233, short circuiting 234, chipping 235and stain 236, etc.) can be detected through cell comparison or chipcomparison in the comparator circuit 17.

[0174] When sampling in which the minimum and maximum values of thepattern are preserved is executed in the A/D converter 15 a, the patterninformation is not damaged even in case of a large detection pixel sizeand high precision defect inspection can be carried out at a high speedin the comparator circuit 17.

[0175] In the embodiments shown in FIGS. 28 to 30, the waveform of thesampled digital image signal indicating the shade (brightness) isdescribed with a one-dimensional grid pattern and it is apparent thatthese embodiments can also apply to a two-dimensional grid pattern.

[0176] The above-described embodiments include the embodiment forinspecting a defect on the pattern formed on the inspected object 1 andthe embodiment of the microscopic observation system for observing thepattern formed on the inspected object 1. The present invention canapply as a fifth embodiment to inspection of impurities which remain onthe pattern formed on the inspected object 1 and measurement of thedimensions of the pattern formed on the inspected object 1.

[0177] As described in the fourth embodiment, for example, the CPU 20can measure the dimensions of the pattern with high accuracy. Impuritieswhich exist on the pattern (LSI wafer pattern) formed on the inspectedobject 1 can be detected as in inspection of defects. In other words,the first order or higher order diffraction lights which have variousdiffraction angles are introduced from impurities into the pupil 10 a ofthe objective lens 9 as in the case of projection defect 231 andchipping defect 236. On the other hand, the 0th order diffraction lightand the + first order diffraction light from the pattern are enteredinto the pupil 10 a of the objective lens 9, different image signals aredetected from the image sensor 12 a, and impurities can be detected bycell comparison or chip comparison executed in the comparator circuit17. Those impurities on a mirror surface wafer can be similarlydetected.

[0178] As described in the following embodiments, the information of thepattern can be erased by using a space filter 309 not erased by cellcomparison or chip comparison. Impurities can be detected according tothe image signals on the pupil 10 a of the objective lens 9 which aredetected by the image sensor 12 b. In other words, the impurities on themirror surface wafer can be directly detected from the image signals onthe pupil 10 a of the objective lens 9 detected by the image sensor 12b. Impurities which exist on the pattern (LSI wafer pattern) formed onthe inspected object 1 can be detected by erasing the patterninformation from the image signals on the pupil 10 a of the objectivelens 9 detected by the image sensor 12 b, since the localitydistribution of the diffraction lights entering into the pupil 10 a ofthe objective lens 9 is different between the impurities and thepattern.

[0179] Specifically, the impurities can be detected by storing thereference image signals on the pupil 10 a obtained from a normal patternon which no impurities exist and which is detected by the image sensor12 b in the delay memory 16, and comparing the stored reference imagesignals on the pupil 10 a and the image signals on the pupil 10 aobtained from the inspected pattern to be actually detected by the imagesensor 12 b to erase the pattern information. The pattern informationcan be erased and the impurities can be detected by masking (shielding)the locality distribution information of the diffraction lights on thepupil 10 a to be obtained from the inspected pattern with the localitydistribution information or the reversed locality distributioninformation (space filter 309 in FIGS. 31 and 33) of the diffractionlights on the pupil 10 a to be obtained from the normal pattern.

[0180] A practical configuration of an optical system for use in thepattern inspection apparatus according to the present invention as asixth embodiment is described with reference to FIGS. 31 and 32, whichrespectively show the practical configuration of the optical system tobe used in the pattern inspection apparatus shown in FIG. 1, whereinFIG. 31 is a plan view and FIG. 32 is a front view thereof.

[0181] The configuration of the optical system shown in FIGS. 31 and 32for use in the pattern inspection apparatus is basically the same as theconfiguration of the optical system shown in FIG. 1 for the patterninspection apparatus. In this embodiment, a television camera TV₁ forannular-looped illumination (bright field illumination) and a televisioncamera TV₂ for dark field illumination as TV cameras for observingimages, and a television camera TV₄ for dark field illumination as a TVcamera for observing the pupil 10 a of the objective lens 9 are added.Accordingly, the TV camera TV₁ for annular-looped illumination (brightfield illumination) and the TV camera TV₂ for dark field illuminationare used to observe the images. The TV camera TV₃ for annular-loopedillumination (bright field illumination) to be used as the TV camera forobserving the pupil 10 a of the objective lens 9 is the same as theimage sensor 12 b.

[0182] Specifically, based on an image (a locality distribution of thediffraction light obtained from the pattern on the inspected object 1with annular-looped illumination) on the pupil 10 a to be picked up bythe TV camera TV₃ (12 b) for annular-looped illumination (bright fieldillumination), the CPU 20 selectively controls a defect detectionsensitivity in the filter (disc type mask: opening diaphragm) 5 forannular-looped illumination, the pupil filter (attenuation filter) 38for controlling the light quantity of the 0th diffraction light or thecomparator circuit 17; a detection pixel size to be obtained fromsampling by the A/D converter 15 a; or a magnification depending on thezoom lens 13. Based on the image (a distribution of scattering light tobe obtained from the pattern on the inspected object 1 with dark fieldillumination described later) on the pupil 10 a to be picked up by theTV camera TV₄ for dark field illumination, the CPU 20 selectivelycontrols an impurity detection sensitivity in the space filter 309 orthe comparator circuit, or the detection pixel size to be obtained fromsampling by the A/D converter for A/D-converting the image signalsobtained from a linear image sensor 308. Thus, the microscopicobservation system can be adapted for the pattern on the inspectedobject 1.

[0183] A dichroic mirror 325 admits to pass a light of the image on thepupil 10 a as the diffraction light to be obtained from the inspectedobject 1 with the annular-looped illumination of 600 nm or under inwavelength, and reflects a light of the image on the pupil 10 a as thescattering light to be obtained from the inspected object 1 with thedark field illumination of 780 to 800 nm in wavelength, which isdescribed later. Reference numerals 326 is a mirror.

[0184] The light house 124′ comprises two types of lamps, that is, aHg—Xe lamp L₁ and a Xe lamp L₂ as the primary light sources 3 and 4shown in FIG. 1 and these two types of the primary light sources areadapted to be changed over by a mirror 317 for changeover. The Hg—Xelamp L₁ has a brightness spectrum and is available for high intensityillumination with a width of short wavelength and the Xe lamp L₂ canprovide incandescent illumination. In other words, for annular-loopedillumination including circular illumination through the filter 5 forannular-looped illumination (secondary light source for annular-loopedillumination: disc type mask: opening diaphragm), the illumination canbe made by changing over high intensity illumination at the width ofshort wavelength using the Hg—Xe lamp L₁ and incandescent illuminationusing the Xe lamp L₂.

[0185] An integrator 318 as shown in FIG. 33, is provided for makinguniform the intensity of light emitted from the Hg—Xe lamp L₁ or the Xelamp L₂ and an intensity monitor 341 is provided for monitoringvariations of the intensity of light in the primary light sources L₁ andL₂. The light quantity control filter 14 is controlled and theconversion level in the A/D converter 15 is compensated, in accordancewith the variations of the intensity in the primary light sources L₁ andL₂ monitored by an intensity monitor 341, as shown in FIG. 33. Awavelength selection filter 316 is provided for selecting the wavelengthof the annular-looped illumination light to, for example, 600 nm orunder. A field diaphragm 319 is provided for shielding a light otherthan the annular-looped illumination and a mirror 301 is also provided.

[0186] A dichroic mirror 320 provided in the front of a second objectivelens 303 is intended to pass the diffraction light obtained from theinspected object 1 with the annular-looped illumination of wavelength of600 nm or under, and reflect a scattering light obtained from theinspected object 1 with the dark field illumination of wavelength of 780to 800 nm described later. There is also provided a half mirror 321 andlenses 326 a and 326 b. A space image formed with a scattering lightproduced from the pattern on the inspected object 1 with the dark fieldillumination of wavelength of 780 to 800 nm is formed at the position ofthe space filter 309. Further, there is provided mirrors 322, 324 and327 and a half mirror 323, as shown in FIG. 33.

[0187] In addition, a dark field illumination optical system (304, 305,306 and 307) for focusing a laser beam emitted from a semiconductorlaser beam source L₃ and slantly irradiating the laser beam onto theinspected object 1 (LSI wafer) is provided so that the impurities can bedetected with high sensitivity. A beam expander 304 (beam expandingoptical system) is provided for the diameter of the laser beam emittedfrom the semiconductor laser beam source L₃ and mirrors 305 and 306 areprovided for reflecting the laser beam while a focusing lens 307 isprovided for focusing the laser beam the diameter of which is expandedand slantly irradiating the laser beam onto the inspected object 1.

[0188] The 0th order diffraction light (positive reflection light)produced from the inspected object 1 with dark field illumination by thedark field illumination optical system (304, 305, 306 and 307) is notentered into the pupil 10 a of the objective lens 9 and only thescattering light (first order or higher order diffraction light)produced from impurities on the inspected object 1 is entered into thepupil 10 a of the objective lens 9 and received by the image sensor 308,which outputs the signals to enable detection of the impurities. A spacefilter 309 is provided which shuts off to erase the scattering light(first order or higher order diffraction light) which is produced fromthe pattern edge on the inspected object 1 with the dark fieldillumination and entered into the pupil 10 a of the objective lens 9.The wavelength of the laser beam emitted from the semiconductor laserbeam source L₃ is an optional wavelength, for example, 780 to 800 nm,different from the wavelength of the annular-looped illumination (brightfield illumination) from the light house 124′.

[0189] In addition, an automatic focus control optical system isprovided to detect the pattern on the inspected object 1 with highaccuracy as the image signals by the image sensor 12 a. This automaticfocus control optical system comprises a light source 310, a filter 313for obtaining a wavelength of 600 to 700 nm, a pattern 315 for automaticfocus (A/F), a projector lens 314 for projecting the pattern 315 for A/Fon the inspected object 1, half mirrors 312 and 313, and sensors S₁ andS₂ arranged in the front and back of focusing plane.

[0190] The surface (pattern surface) of the inspected object 1 isfocused with the objective lens (imaging optical system) 9 by slightlycontrolling the inspected object 1 in the vertical direction as shownwith an arrow mark so that the contrast signals of the A/F pattern 315,which is projected onto the inspected object 1 by the projector lens314, are respectively detected by the sensors S₁ and S₂, and thecontrast signal obtained from the sensor S₁ coincides with the contrastsignal obtained from the sensor S₂. The dichroic mirror 302 provided inthe light path of the detection optical system reflects a light of 600to 700 nm in wavelength for automatic focusing and admits to pass alight of 600 nm or under in wavelength for annular-looped illumination(bright field illumination) and a light of 750 nm or over in wavelengthfor dark field illumination.

[0191]FIGS. 33 and 34 respectively show further in detail theconfiguration of the optical system in the pattern inspection apparatusshown in FIGS. 31 and 32. FIG. 33 is a plan view and FIG. 34 is a frontview. In other words, an infinite compensation type objective lens 9 isused and therefore a second objective lens (also referred to as tubelens) 303 with a long focal distance (for example, f=200 nm) isrequired. The linear image sensor 12 a for annular-looped illumination(bright field illumination) and the linear image sensor 308 for darkfield illumination are formed with a TDI (Time Delay & Integration) typeimage sensor.

[0192] In this embodiment, a polarization beam splitter (PBS) 8 a′ and aλ/4 plate (¼ wavelength plate) 51 are provided between the objectivelens 9 and a second objective lens 303. Since the lights remain parallelbetween the objective lens 9 and the second objective lens 303, anydeterioration such as aberration is not caused even though the aboveoptical elements 8 a′ and 51 are inserted. The functions of the PBS 8 a′and the λ/4 plate 51 are as shown in FIGS. 35 and 36. Of circularillumination light or annular-looped illumination light 330, Ppolarization light passes through the PBS 8 a′ and S polarization lightis reflected to reach the λ/4 plate 51. The S polarization light 332,which has reached the λ/4 plate 51 to include a component the phase ofwhich is delayed equivalent to 90 degrees (the refractive indexes of anextraordinary ray and an ordinary ray are unequal and the length of theoptical path of the extraordinary ray is longer than the latter.Therefore, a phase difference π/2 occurs between the extraordinary rayand the ordinary ray and the amplitudes of these rays are equal.), isconverted to circular polarization light or elliptical polarizationlight 334 and irradiated onto a wafer which is the inspected object 1through the objective lens 9.

[0193] The diffraction light (reflection light) entering into the pupil10 a of the objective lens 9 reaches again the λ/4 plate 51 and thecircular polarization light or the elliptical polarization light becomesthe P polarization light 333. This P polarization light 333 transmitsthrough the PBS 8 a′ and the second objective lens 303 and reaches theimage sensor 12 a as the detector. FIG. 36 indicates that, when theangle ω to the λ/4 wavelength plate 51 (angle formed by the linearpolarization plane of the incident light and the main cross section ofthe wavelength plate 51) of the incident light (S polarization light)332, which is converted to the linear polarization light by the PBS 8a′, is accurately 45° (+ or −), the incident light 332 of linearpolarization can be converted to the circular polarization light 334 (orvice versa). When the angle ω is other than 45°, the linear polarizationlight is converted to the elliptical polarization light 334 (or viceversa).

[0194]FIGS. 37 and 38 show the effects of this embodiment. The inspectedobject 1 is a pattern comprising lines and spaces of a 256 Mb DRAM (ahigh density grid pattern with pitch P of 0.61 μm). FIG. 37 shows thebrightness (detection intensity) of the pattern received by the imagesensor 12 a to the rotating direction of the above pattern. The circularpolarization annular-looped illumination (including ellipticpolarization annular-looped illumination) in FIG. 37 are based on theembodiments shown in FIGS. 31 to 34. The linear polarizationillumination in the diagram corresponds to the illumination having noλ/4 plate 51. The half mirror in the diagram indicates an illumination(illumination using the λ/4 plate 51) for which a typical half mirror isused instead of the PBS 8 a′.

[0195] From the relationship shown in FIG. 37, it is apparent that theimage signals having high brightness (detection intensity) can beobtained from the image sensor 12 a without being largely affected bythe directionality of the pattern, by applying the circular polarizationannular-looped illumination (including the elliptical polarizationannular-looped illumination) even though a high density pattern on theinspected object 1 has various rotation angles as a memory cell patternas shown in FIG. 24. By using the annular-looped illumination, whetherlinear polarization illumination (S polarization illumination) or halfmirror illumination (using the λ/4 plate 51), the image signals havinghigher brightness (detection intensity) can be obtained from the patternformed on the inspected object 1 which has a peripheral circuit parthaving a special directionality as compared with application of the onlyordinary circular illumination.

[0196] It is apparent that the half mirror illumination (using the λ/4plate 51) is superior to the linear polarization illumination (Spolarization illumination). That the image signals having a highbrightness (detection intensity) can be obtained from the image sensor12 a as described above means that highly efficient illumination for thehigh density pattern can be implemented.

[0197]FIG. 38 shows a contrast (a ratio of the minimum value to themaximum value indicating the resolution) from the pattern received bythe image sensor 12 a in the rotating direction of the pattern. In FIG.38, the circular polarization annular-looped illumination (includingelliptical polarization annular-looped illumination) is based on theembodiments shown in FIGS. 31 to 34. In the diagram, there is onlycircular polarization illumination, and linear polarization illuminationcorresponds to S polarization illumination without the λ/4 plate 51.

[0198] In case of circular polarization annular-looped illumination, thecontrast to the angle of the pattern is not fixed because completecircular polarization is not obtained in the experiment and ellipticalpolarization appears. The ellipticity can be reduced to obtain a truecircle by entering a linear polarization incident light into an opticalelement (λ/4 plate 51) (the direction of electric vector oscillation isaligned in parallel with or normal to the incident plane) and circularpolarization is used by using the phase plate before entry into theinspected object 1.

[0199] From the relationship shown in FIG. 38, it is apparent that theimage signals having a high contrast (high resolution) can be obtainedfrom the image sensor 12 a without being largely affected by thedirectionality of the pattern, by applying the circular polarizationannular-looped illumination (including the elliptical polarizationannular-looped illumination) even though a high density pattern on theinspected object 1 has various rotation angles as a memory cell patternas shown in FIG. 24.

[0200] Those image signals having a high contrast can always be obtainedfrom the image sensor 12 a without depending on the direction of thehigh density pattern, by simultaneously using circular polarizationillumination and annular-looped illumination and consequently micro finedefects on the high density pattern can be detected. The image signalshaving a high contrast (high resolution) can be obtained from simplecombination of normal circular illumination and circular polarizationillumination (only circular polarization illumination) without beinglargely affected by the directionality of the high density pattern fromthe image sensor 12 a as compared with the normal circular illumination.The image signals having a higher contrast (high resolution) than incase of only circular polarization illumination can be obtained bysimultaneously using the circular polarization illumination and theannular-looped illumination.

[0201] By using the annular-looped illumination, the image signalshaving the high contrast (high resolution) can be obtained from a highdensity pattern which is formed on the inspected object 1 and has aspecial directionality as the peripheral circuit part even with thelinear polarization illumination (S polarization illumination). However,In cases of general super LSIs (VLSI and ULSI) on which high densitypatterns are provided and therefore it is difficult to irradiate thelinear polarization light to these patterns at all times in accordancewith the directions of high density patterns. If the patterns have aspecified directionality as a specified wiring pattern, it is necessaryto control the polarization in the linear polarization illumination tobe aligned with the direction of the wiring pattern and to limit thelinear polarization illumination only to the specified wiring pattern.In doing so, the image signals having the high contrast can be detectedfrom the image sensor 12 a.

[0202] Though the PBS 8 a′ is used in the description of the aboveembodiments, similar effects can be obtained by using the half mirrorwhich is coated with a dielectric multi-layer film. A polarization platecan be used to obtain the linear polarization illumination instead ofthe PBS 8 a′. In this case, the quantity of light passing through thepolarization plate is attenuated and the brightness (detectionintensity) is decreased but the contrast is improved as in case of thePBS 8 a′.

[0203] In a seventh embodiment of the present invention, a diffusionplate for diffusing light is inserted into the position (position inconjunction with the pupil 10 a of the objective lens 9) of the fielddiaphragm 319 or the filter (opening diaphragm) 5 for annular-loopedillumination. This diffusion plate is specified with the sand No. 800.Such diffusion plate serves to increase a diffusibility of theillumination light in irradiation of only the annular-loopedillumination light or simultaneous irradiation of the polarizedillumination and the annular-looped illumination to the inspected object1, and a bright and uniform reflection light can be obtained in spite ofthe variation of the surface of metallic wiring pattern, such as finerecesses and projections and therefore the surface of the metallicwiring pattern can be detected or observed as the image having uniformbrightness by the image sensor 12 a or the TV camera TV₁ for brightfield observation through the objective lens 9.

[0204] This diffusion illumination is not compatible with annular-loopedillumination and polarization illumination and can be simultaneouslyimplemented in the same optical system. The extent of diffusion isselected in accordance with the pattern on the inspected object 1.

[0205] In the embodiments shown in FIGS. 31 to 34, the image sensor 12 ais formed with the TDI (Time Delay & Integration) type image sensor and,if the reflectivity of the pattern of the inspected object 1 is low andthe brightness (detection intensity) is insufficient, the image sensorcan be controlled to increase its accumulation time. Thus, theaccumulation time of the image sensor can be appropriately determined inaccordance with the pattern of the inspected object 1. Furthermore, theaccumulation time of the image sensor can be determined according to theilluminating conditions for the pattern of the inspected object 1.

[0206] The following describes analyses of the causes of defects, forexample in semiconductor manufacturing processes as shown in an eighthembodiment of the present invention as illustrated in FIG. 39, byentering defect determination output 18 to be outputted from thecomparator circuit 17 of the apparatus shown in FIG. 1 and defectinformation 40 to be outputted from the CPU 20, and production of highquality semiconductor chips at a high yield by eliminating the analyzedcauses of defects.

[0207] As shown in FIG. 39, there is provided a semiconductormanufacturing line 380 with a conveying path 381 for a semiconductorwafer 1 a. A CVD unit 382 is provided for executing a CVD film formingstep for forming an insulation film and a sputtering unit 383 isprovided for executing a sputtering step for forming a wiring film ofthe semiconductor steps. An exposure unit 384 is provided for executingexposure steps for application of resist, exposure and development ofthe semiconductor manufacturing steps and an etching unit 385 isprovided for executing an etching step for patterning of thesemiconductor manufacturing steps. Thus, semiconductor wafers aremanufactured through various manufacturing steps.

[0208] A computer 390 is provided for analyzing the causes of defects orfactors of defects in the manufacturing line 380 comprising the processunits 382, 383, 384 and 385 for manufacturing the above-describedsemiconductors by entering defect determination output 18 outputted fromthe comparator circuit 17 and defect information 40 outputted from theCPU 20 shown in FIG. 1. The computer 390 for analysis comprises aninterface 391 for entering the defect determination output 18 outputtedfrom a comparator circuit 17 and the defect information 40 outputtedfrom the CPU 20 shown in FIG. 1; a CPU 392 for executing processing suchas analysis; a memory 393 which stores programs such as for analysis;control circuits 394, 395, 396 and 397; an output unit 398 such as aprinting unit for outputting the results of analysis such as causes ofdefects; a display unit 399 for displaying various data; an input unit(comprising a keyboard, a disc and others) 401 for entering data relatedto, for example, process units 382, 383, 384 and 385 which cannot beobtained from the units shown in FIG. 1 and data related to thesemiconductor wafer 1 a to be supplied to the manufacturing line 380; anexternal storage unit 402 which stores history data of correlationbetween defects which occur on the semiconductor wafer 1 a and thecauses of defects or the factors of defects due to which a defect iscaused in the manufacturing line 380 which comprises process units 382,383, 384 and 385, or a data base; an interface 403 for supplyinginformation 410 related to the causes of defects or the factors ofdefects analyzed by the CPU 392 to the process units 382, 383, 384 and385; and a bus line 400 for connecting these component units.

[0209] The CPU 392 in the computer 390 for analysis analyzes the causesof defects or the factors of defects due to which a defect is caused inthe manufacturing line 380 which comprises process units 382, 383, 384and 385 according to the defect determination output 18 and the defectinformation 40, and the history data of correlation between defects onthe semiconductor wafer 1 a and the causes of defects or the factors ofdefects in the manufacturing line 380 or a data base, which are storedin the external storage unit 402, and supplies the information 410related to the analyzed cause or factor of defect to the process units382, 383, 384 and 385.

[0210] The process units 382, 383, 384 and 385 to which the information410 related to the causes of defects or the factors of defects issupplied can feed a satisfactory semiconductor wafer 1 a to a followingprocess by controlling various process conditions including cleaning,and by eliminating the causes of defects or the factors of defects andconsequently manufacture semiconductors at a high yield. Thesemiconductor wafer 1 a, a defect of which is inspected by the apparatusshown in FIG. 1, is sampled in a unit of the semiconductor wafer 1 a ora lot thereof in the front and rear processes where the defect is liableto be caused in the manufacturing line 380.

[0211] The CPU 392 in the computer 390 for analysis analyzes the causesof impurities or the factors of impurities due to which an impurity iscaused in the manufacturing line 380 according to impurity informationobtained from and entered by the CPU 20 in accordance with an impuritysignal detected by an image sensor 308, and the history data ofcorrelation between the impurities on the semiconductor wafer 1 a andthe causes of impurities or the factors of impurities due to which animpurity is formed in the manufacturing line 380 or a data base, whichare stored in the external storage unit 402, and supplies theinformation 410 related to the analyzed cause or factor of impurity tothe process units 382, 383, 384 and 385.

[0212] The process units 382, 383, 384 and 385 to which the information410 related to the causes of impurities or the factors of impurities issupplied can feed a defect-free semiconductor wafer 1 a to a followingprocess by controlling various process conditions including cleaning,and by eliminating the causes of impurities or the factors of impuritiesand consequently manufacture semiconductors at a high yield.

[0213] The present invention enables inspection with high reliability ofmicro fine defects which occur on micro fine patterns formed on asemiconductor substrate having micro fine patterns such as asemiconductor wafer, a TFT substrate, a thin film multi-layer substrateand a printed board, and to manufacture semiconductor substrates at ahigh yield by feeding back the results of inspection to themanufacturing processes for semiconductor substrates. In addition, thepresent invention is adapted to detect defects on micro fine patterns bydetecting high resolution image signals from micro fine patterns on theinspected object with annular-looped illumination applied thereto,comparing these high resolution image signals with the reference highresolution image signals and erasing micro fine patterns according toconsistency of these image signals to detect the defects on the microfine patterns and therefore, provides an effect to inspect the defectson micro fine patterns in high reliability.

[0214] The present invention is adapted to irradiate the annular-loopedillumination onto micro fine patterns on the inspected object, attenuateat least part of the 0th order diffraction light of the 0th orderdiffraction light and the first order diffraction light (+ first orderdiffraction light or − first order diffraction light), which areproduced from the micro fine pattern and entered into the pupil of theobjective lens, by the filter for controlling the light quantity whichis provided at a position in conjunction with the pupil of the objectivelens, receive the 0th order diffraction light and the first orderdiffraction light, detect image signals of high resolution from themicro fine pattern, compare the high resolution image signals with thereference high resolution image signals, erase the micro fine patternaccording to consistency of these image signals, and detect the defectson the micro fine pattern, and therefore provides an effect to inspectthe defects on micro fine patterns in high reliability. Further, thepresent invention enables detection of the images or image signals fromthe micro fine patterns in a high resolution (resolution power) and alarge difference of shade (brightness), by simultaneously using theannular-looped illumination and the polarization illumination(particularly, circular or elliptic polarization illumination isexcellent) for micro fine patterns on the inspected object. The presentinvention provides an effect enabling to detect the images or imagesignals from the micro fine patterns having various directionalities ina high resolution (resolution power) and a large difference of shade(brightness), by simultaneously using the annular-looped illuminationand the polarization illumination (particularly, dircular or ellipticpolarization illumination is excellent) for micro fine patterns havingvarious directionalities on the inspected object.

[0215] The present invention is adapted to detect the image signalshaving a high resolution (resolution power) and a large difference ofshade (brightness) from the micro fine patterns having variousdirectionalities on the inspected object by simultaneously using theannular-looped illumination and the polarization illumination(particularly, circular or elliptic polarization illumination isexcellent) for micro fine patterns, compare these image signals with thereference image signals having a high resolution (resolution power) anda large difference of shade (brightness), erase the micro fine patternshaving various directionalities according to consistency of these imagesignals, to detect the defects on the micro fine patterns having variousdirectionalities, and therefore provides an effect of inspecting thedefects of micro fine patterns having various directionalities in highreliability.

[0216] The present invention enables detection of images or imagesignals with a high resolution (resolution power) adapted to a microfine pattern by detecting an image based on a diffraction light which isproduced from a micro fine pattern on the inspected object and enteredinto the pupil of the objective lens, controlling the annular-loopedillumination (for example, OUT σ and IN σ) according to this image, andapplying this controlled annular-looped illumination to the micro finepattern on the inspected object. Further, the present invention isadapted to detect the defects on the micro fine pattern by detecting animage based on a diffraction light which is produced from a micro finepattern on the inspected object and entered into the pupil of theobjective lens, controlling the annular-looped illumination (forexample, OUT σ and IN σ) according to this image, applying thiscontrolled annular-looped illumination to the micro fine pattern on theinspected object to detect the image signals of a high resolution(resolution power) adapted to a micro fine pattern, comparing theseimage signals having a high resolution with the reference image signalshaving a high resolution, and erasing the micro fine pattern accordingto consistency of these image signals to detect the defects on the microfine pattern and therefore provides an effect enabling to inspect thedefects on the micro fine pattern in high reliability.

[0217] Additionally, the present invention enables detection of imagesor image signals with a high resolution (resolution power) adapted to amicro fine pattern by identifying (observing or detecting) a localitydistribution of the 0th order diffraction light and the first orderdiffraction light (+ first order or − first order diffraction light)which are produced from a micro fine pattern on the inspected object andentered into the pupil of the objective lens, controlling theannular-looped illumination (for example, OUT σ and IN σ) according tothis identified (observed or detected) locality distribution of thediffraction light, and applying this controlled annular-loopedillumination to the micro fine pattern on the inspected object.

[0218] The present invention is adapted to identify (observe or detect)a locality distribution of the 0th order diffraction light and the firstorder diffraction light (+ first order or − first order diffractionlight) which are produced from a micro fine pattern on the inspectedobject and entered into the pupil of the objective lens, control theannular-looped illumination (for example, OUT σ and IN σ) according tothis identified (observed or detected) locality distribution of thediffraction light, apply this controlled annular-looped illumination tothe micro fine pattern on the inspected object to detect image signalsof a high resolution (resolution power) adapted to the micro finepattern, compare this high resolution image signal with the referencehigh resolution image signal, and erase the micro fine pattern accordingto consistency of these image signals to detect the defects on the microfine pattern and therefore provides an effect enabling to inspect thedefects on the micro fine patterns in high reliability.

[0219] Further, the present invention is adapted to detect image signalswith a high resolution (resolution power) adapted to a micro finepattern by detecting an image showing a density of the micro finepattern based on the diffraction light which is produced from the microfine pattern on the inspected object and entered into the pupil of theobjective lens, controlling the annular-looped illumination (forexample, OUT σ and IN σ) according to this image, and applying thiscontrolled annular-looped illumination to the micro fine pattern on theinspected object, and by comparing this high resolution image signalwith the reference high resolution image signal and erasing the microfine pattern according to consistency of these image signals to detectthe defects on the micro fine pattern and therefore provides an effectenabling to inspect the defects on the micro fine patterns in highreliability.

[0220] While we have shown and described several embodiments inaccordance with the present invention, it is understood that the same isnot limited thereto but is susceptible of numerous changes andmodifications as known to those skilled in the art, and we therefore donot wish to be limited to the details shown and described herein butintend to cover all such changes and modifications as are encompassed bythe scope of the appended claims.

What is claimed is:
 1. A method for detecting information relating to apattern on an object to be inspected comprising the steps of: focusingand irradiating an annular-looped diffusion illumination light formedwith a plurality of virtual spot light sources onto a pattern on theobject to be inspected through a pupil of an objective lens; receivingan image of the pattern of the inspected object by focusing a first orsecond order diffraction light including a 0th order diffraction lightwhich is reflected from the pattern on the inspected object by thefocused and irradiated annular-looped diffusion illumination light andentered into the pupil of the objective lens; and converting thereceived image of the pattern of the inspected object to image signalsof the pattern for obtaining information relating to the pattern.
 2. Amethod according to claim 1, wherein the image signals of the patternprovide information relating to a defect of the pattern.
 3. A methodaccording to claim 1, wherein the step of receiving an image of thepattern includes utilization of an image sensor, and further comprisingthe steps of comparing the image signals of the pattern of the inspectedobject with image signals of a reference pattern, erasing the pattern ofthe inspected object according to consistency of the received imagesignals and the image signals of the reference pattern, and detecting adefect of the pattern according to an inconsistency.
 4. A methodaccording to claim 1, wherein at least one of the step of focusing andirradiating and the step of receiving includes utilizing a lightquantity control filter for partly changing an intensity or a quantityof the first or second order diffraction light including a 0th orderdiffraction light entered into the pupil of the objective lens andreflected from the pattern, the step of receiving further includesutilizing an image sensor, and further comprising detecting the patternon the inspected object according to the converted image signals of thepattern.
 5. A method according to claim 4, further comprising the stepsof comparing the converted image signals of the pattern with imagesignals of a reference pattern, erasing the pattern of the inspectedobject according to consistency of the received image signals and theimage signals of the reference pattern, and detecting a defect accordingto an inconsistency.
 6. A method according to claim 4, wherein the stepof receiving includes utilizing a first image sensor, further comprisingthe steps of controlling the annular-looped diffusion illumination lightaccording to image signals of the pupil obtained by receiving the imageon the pupil of the objective lens with a second image sensor.
 7. Amethod according to claim 6, further comprising the step of convertingthe image received by the second image sensor.
 8. A method according toclaim 6, wherein the steps of controlling include receiving with thesecond image sensor the image of a distribution of a locality of thediffraction lights including the 0th order diffraction light enteredinto the pupil of the objective lens.
 9. A method according to claim 6,further comprising the steps of comparing the image signals of thepattern obtained from the first image sensor with image signals of areference pattern, erasing the pattern of the inspected object accordingto consistency of the image signals received by the first image sensorand the image signals of the reference pattern, and detecting a defectof the pattern according to inconsistency of the compared image signals.10. A method according to claim 8, further comprising the steps ofcomparing the image signals of the pattern obtained from the first imagesensor with image signals of a reference pattern, erasing the pattern ofthe inspected object according to consistency of the image signalsobtained from the first image sensor with the image signals of thereference pattern, and detecting a defect of the pattern according toinconsistency of the compared image signals.
 11. A method according toclaim 1, further comprising the step of detecting the pattern on theobject to be inspected according to the converted image signals of thepattern.
 12. A method according to claim 1, wherein the step of focusingand irradiating includes focusing and irradiating a polarizationannular-looped diffusion illumination light formed by adding apolarization to the annular-looped diffusion illumination light formedwith the plurality of virtual spot light sources onto the pattern, anddetecting the pattern on the object to be inspected according to theimage signals of the pattern.
 13. A method according to claim 12,wherein the polarization is one of circular and elliptical polarization.14. A method according to claim 1, wherein the step of focusing andirradiating includes focusing and irradiating a polarizationannular-looped diffusion illumination light formed by adding apolarization to the annular-looped diffusion illumination light formedwith the plurality of virtual spotlight sources onto the pattern, andfurther comprising the steps of comparing the image signals of thepattern of the inspected object with image signals of a referencepattern, erasing the pattern of the inspected object according toconsistency of the image signals of the pattern and the image signals ofthe reference pattern, and detecting a defect of the pattern accordingto inconsistency of the compared image signals.
 15. A method accordingto claim 14, wherein the polarization is one of circular and ellipticalpolarization.
 16. A method according to claim 3, further comprising thesteps of receiving with the image sensor an image of an impurity on thepattern on the inspected object obtained by focusing a scattering lightwhich is reflected from an impurity on the inspected object with a darkfield illumination irradiated onto the pattern on the inspected objectand entered into the pupil of the objective lens, converting thereceived image to the signals indicating the impurity, and detectingimpurity information of the pattern.
 17. A semiconductor substratemanufacturing method for manufacturing semiconductor substratesrespectively having a pattern or patterns in a manufacturing linecomprising various process units, comprising the steps: performinghistory data or data based build-up by accumulating in advance of apresent step of manufacturing information of a pattern defect whichoccurred on the semiconductor substrate and history data or a data basewhich indicates a correlation between a defect and a cause of defect ora factor of defect which incurs a defect of a pattern in themanufacturing line and building up the history data or the databasewhich indicates the correlation; performing defect inspection utilizingthe method according to claim 1 for detecting defect information of apattern on an inspected object which is a semiconductor substrate,wherein the focused and irradiated annular-looped diffusion illuminationlight is irradiated to the semiconductor substrate which reaches aspecified position on the manufacturing line, obtaining the convertedimage signals and comparing the received converted image signals of thepattern with image signals of a reference pattern for detecting defectinformation; analyzing a cause of a defect or a factor of a defect whichincurs a defect of the pattern in an upstream manufacturing line fromthe specified position of the manufacturing line according to theinformation of the pattern defect which occurs on the semiconductorsubstrate as detected and the history data or the database which isbuilt up in the history data or database built-up step and indicates acorrelation between the information of a pattern defect and a cause of adefect or a factor of a defect; and controlling process conditions inthe upstream manufacturing line for eliminating the cause of a defect orthe factor of the defect which has been analyzed in the defect causeanalyzing step.
 18. A semiconductor substrate manufacturing methodaccording to claim 17, wherein the inspection step includes controllingthe annular-looped diffusion illumination light focused and irradiatedonto the pattern on the semiconductor substrate, and receiving a highresolution image of the pattern.
 19. A semiconductor substratemanufacturing method according to claim 18, wherein in the inspectionstep, the focused and irradiated annular-looped diffusion illuminationlight is controlled according to the image on a pupil of the objectivelens.
 20. A semiconductor substrate manufacturing method according toclaim 17, wherein in the inspection step, the annular-looped diffusionillumination light which is focused and irradiated is a polarizedannular-looped diffusion illumination light formed by addingpolarization to the annular-looped diffusion light.
 21. A semiconductorsubstrate manufacturing method according to claim 20, wherein in theinspection step, the polarized annular-looped diffusion light is one ofcircular and elliptical polarization.
 22. A semiconductor substratemanufacturing method according to claim 17, further comprising animpurity inspection step for detecting an impurity on the pattern byirradiating a dark field illumination onto the semiconductor substratewhich has reached the specified position on the manufacturing line,receiving an image of an impurity of the pattern of the inspected objectobtained by focusing a scattering light which is reflected from animpurity on the pattern of the inspected object and entered into thepupil of the objective lens with an image sensor, and converting thereceived image signals indicating the impurity, the analyzing stepincluding analyzing a cause of at least one of a defect and impurity ora factor of at least one of a defect or impurity which incurs a defector an impurity of the pattern in the upstream manufacturing line fromthe specified position of the manufacturing line in accordance with thedefect information of the pattern detected in the defect inspection stepand the impurity information of the pattern detected in the impurityinspection step and the history data or the data base which is built upin the history data or data base build-up step and indicates thecorrelation of causes and results, and the controlling processconditions step includes controlling process conditions in the upstreammanufacturing line for eliminating the cause of at least one of thedefect and impurity or a factor of at least one of the defect andimpurity analyzed in the at least one of the defect and impurity causeanalyzing step.
 23. A pattern detection apparatus for detecting apattern on an object to be inspected, comprising: illumination means foremitting an annular-looped diffusion illumination light formed with aplurality of virtual spot light sources; an illumination optical systemfor focusing and irradiating the emitted annular-looped diffusion lightonto a pattern on an inspected object through a pupil of an objectivelens; and a detection optical system for receiving with an image sensor,an image of the pattern on the inspected object obtained by focusing afirst or second order diffraction light including a 0th orderdiffraction light which is reflected from the pattern on the inspectedobject by the focused and irradiated annular-looped diffusionillumination light from the illumination optical system and entered intothe pupil of the object lens, and for converting the received image ofthe pattern to image signals of the patter for obtaining informationrelating to the pattern.
 24. A pattern detection apparatus according toclaim 25, further comprising comparison means for comparing theconverted image signals of the pattern with image signals of a referencepattern; means for erasing the pattern of the inspected object accordingto consistency of the received converted image signals and the imagesignals of the reference pattern; and means for detecting a defectaccording to an inconsistency.
 25. A pattern detection apparatusaccording to claim 24, wherein at least one of the illumination opticalsystem and the detection optical system includes a light quantitycontrol filter for partly changing the intensity or the light quantityof the first or second order diffraction light, including the 0th orderdiffraction light which is reflected from the pattern.
 26. A patterndetection apparatus according to claim 25, wherein the detection opticalsystem includes the light quantity control filter for partly controllingthe light quantity of the 0th order diffraction light which is reflectedfrom the pattern.
 27. A pattern detection inspection apparatus accordingto claim 23, wherein the detection optical system includes means forenabling variable optical magnification therein.
 28. A pattern detectioninspection apparatus according to claim 23, further comprising a pupildetection optical system for receiving with another image sensor, theimage on the pupil of the objective lens from the another sensor and forconverting the received image to image signals of the pupil; and controlmeans for controlling the annular-looped diffusion illumination lightemitted by the illumination means according to the image signals of thepupil obtained from the another image sensor of the pupil detectionoptical system.
 29. A pattern detection apparatus according to claim 28,wherein the detection optical system includes means for varying opticalmagnification therein.
 30. A pattern detection apparatus according toclaim 23, further comprising a pupil detection optical system forreceiving with another image sensor a distribution of locality ofdiffraction light including the 0th order diffraction light and forconverting the received image to image signals of the pupil; and controlmeans for controlling the annular loop diffusion illumination lightemitted by the illumination means according to the image signals of thepupil obtained from the another image sensor of the pupil detectionoptical system.
 31. A pattern detection apparatus according to claim 30,wherein the detection optical system includes means for varying anoptical magnification therein.
 32. A pattern detection apparatusaccording to claim 23, wherein the illumination optical system includespolarization means having polarization conversion optical elements foradding polarization to the annular-looped diffusion illumination lightemitted from the illumination means.
 33. A pattern detection apparatusaccording to claim 3e, wherein the polarization means includes one ofcircular and elliptical polarization conversion optical elements forapplying one of circular and elliptical polarization to the emittedannular-looped diffusion illumination light.
 34. A pattern detectionapparatus according to claim 23, further comprising another illuminationoptical system for irradiating a focused dark field illumination to thepattern on the inspected object, another detection optical system forreceiving light from an impurity on the pattern on the inspected objectobtained by focusing a scattering light which is reflected from thepattern on the inspected object irradiated by the another illuminationoptical system and entered into the pupil of the objective lens, and forconverting the received light to signals indicative of the impurity, andfurther comprising comparison means for comparing the image signals ofthe pattern obtained from the detection optical system with imagesignals of a reference pattern, means for erasing the pattern of theinspected object according to consistency of the image signals of thepattern and image signals of the reference pattern, and means fordetecting a defect of a pattern according to an inconsistency, andimpurity detection means for detecting impurity information according tothe signal obtained from the another detection optical system.
 35. Apattern detection apparatus according to claim 34, wherein theillumination optical system includes polarization means for addingpolarization to the annular-looped diffusion illumination light emittedby the illumination means and including polarization conversion opticalelements.
 36. A pattern detection apparatus according to claim 35,wherein the polarization means includes means for adding one of circularand elliptical polarization and including one of circular and ellipticalpolarization conversion optical elements.
 37. A pattern detectionapparatus according to claim 23, wherein the pattern detection apparatusis part of a microscope system.
 38. A pattern detection apparatusaccording to claim 23, wherein the pattern detection apparatus is partof a manufacturing system for manufacturing semiconductors and theobject to be inspected is a semiconductor substrate having the patternthereon.
 39. A pattern defect inspection apparatus for detecting adefect of a pattern on an object to be inspected comprising:illuminating means for irradiating a uniform illumination light in adetection field of an object to be inspected through an objective lens;image detection means for detecting and converting a reflected lightfrom the inspected object to an image by photoelectric conversion; andimage comparison means for comparing the detection image with areference image.
 40. A pattern defect inspection apparatus according toclaim 39, wherein the image detection means includes pupil imagedetection means for forming an image on the pupil of the objective lensthrough a lens and for detecting the image thereof.
 41. A pattern defectinspection apparatus according to claim 39, further comprisingpolarization state control means for controlling a state of polarizationof the illumination light emitted by the illuminating means.
 42. Apattern defect inspection apparatus according to claim 40, furthercomprising polarization state control means for controlling a state ofpolarization of the illumination light emitted by the illuminatingmeans.